Los Angeles, California, has the largest concentration of Scientologists and Scientology-related organizations in the world, with the Church of Scientology's most visible presence being in the Hollywood district of the city. The organization owns a former hospital on Fountain Avenue which houses Scientology's West Coast headquarters, the Pacific Area Command Base – often referred to as "PAC Base" or "Big Blue", after its blue paint job. Adjacent buildings include headquarters of several internal Scientology divisions, including the American Saint Hill Organization, the Advanced Organization of Los Angeles, and the Church of Scientology of Los Angeles. All these organizations are integrated within the corporation Church of Scientology Western United States. The Church of Scientology successfully campaigned to have the city of Los Angeles rename one block of a street running through their complex "L. Ron Hubbard Way". The street has been paved in brick.

Scientology's Celebrity Center International is located on Franklin Avenue, while the Association for Better Living and Education, Author Services, the Test Center, and the official headquarters of the Church of Scientology International (in the Hollywood Guaranty Building) are all located on Hollywood Boulevard. The ground floor of the Guaranty Building also features the L. Ron Hubbard Life Exhibition, a museum detailing his life that is open to the general public. The Celebrity Centre was acquired by the organization as the Chateau Elysee in 1973, built to accommodate members in the arts, sports and government.

The headquarters of Religious Technology Center, the entity that oversees Scientology operations worldwide, is located in unincorporated Riverside County, California, near the city of San Jacinto. The facility, known as Gold Base or "Int", is owned by Golden Era Productions and is the home of Scientology's media production studio, Golden Era Studios. Several Scientology executives, including David Miscavige, live and work at the base. Therefore, Gold Base is Scientology's international administrative headquarters.

The Church of Scientology bought the former Gilman Hot Springs resort, which had been popular with Hollywood figures, in 1978; the resort became Gold Base. The facilities are surrounded by floodlights and video observation cameras, and the compound is protected by razor wire.

The Church of Scientology maintains a large base on the outskirts of Trementina, New Mexico, for the purpose of storing their archiving project: engraving Hubbard's writings on stainless steel tablets and encasing them in titanium capsules underground. An aerial photograph showing the base's enormous Church of Spiritual Technology symbols on the ground caused media interest and a local TV station broke the story in November 2005. According to a report in The Washington Post, the organization unsuccessfully attempted to coerce the station not to air the story.

It is difficult to obtain reliable membership statistics. In the US, the 2008 American Religious Identification Survey found that there were 25,000 Scientologists in the US. Some of these were not considered to be members of the organization. A 2008 Trinity College survey similarly concluded there were 25,000 Scientologists. The International Association of Scientologists (IAS), the official Church of Scientology membership system since 1984, has never released figures. The organization's spokespersons either give numbers for their countries or a worldwide figure.

The organization has said that it has eight to fifteen million members worldwide, but this figure is known to be an aggrandizing fabrication. Religious scholar J. Gordon Melton has said that the organization's estimates of its membership numbers are exaggerated: "You're talking about anyone who ever bought a Scientology book or took a basic course. Ninety-nine percent of them don't ever darken the door of the church again." Melton has stated that if the claimed figure of 4 million American Scientologists were correct, "they would be like the Lutherans and would show up on a national survey".

Statistics from other sources:

• In 2001, the American Religious Identification Survey (ARIS) reported that there were 55,000 adults in the United States who consider themselves Scientologists. A 2008 survey of American religious affiliations by the US Census Bureau estimated there to be 25,000 Americans identifying as Scientologists.
• The 2001 United Kingdom census contained a voluntary question on religion, to which approximately 48,000,000 chose to respond. Of those living in England and Wales who responded, a total of 1,781 said they were Scientologists.
• In 2011, Statistics Canada, the national census agency, reported a total of 1,745 Scientologists nationwide, up from 1,525 in 2001 and 1,220 in 1991.
• In 2005, the German Office for the Protection of the Constitution estimated a total of 5,000 – 6,000 Scientologists in that country, and mentioned a count of 12,000 according to Scientology Germany.
• In the 2006 New Zealand census, 357 people identified themselves as Scientologists, although a spokesperson for the organization said there were between 5,000 and 6,000 Scientologists in the country. Earlier census figures were 207 in the 1991 census, 219 in 1996, and 282 in 2001.
• In 2006, Australia's national census recorded 2,507 Scientologists nationwide, up from 1,488 in 1996, and 2,032 in 2001. The 2011 census however found a decrease of 13.7 percent from the 2006 census.
• In 2011, SonntagsZeitung reported that support for Scientology in Switzerland had experienced a steady decline from 3,000 registered members in 1990 to 1,000 members and the organization was said to be facing extinction in the country. A Church of Scientology spokesperson rejected the figures claiming that the organization had 5,000 "passive and active members in Switzerland".
• In 2011, the "Scientology Association of Finland" had approximately 120 members.

In 2008, the Church of Scientology and its large network of corporations, nonprofits and other legal entities were estimated to bring in around 500 million US dollars in annual revenue. Scientologists can attend classes, exercises or counseling sessions for a set range of "fixed donations"; however, membership without courses or auditing is possible. According to a sociological report entitled "Scientology: To Be Perfectly Clear", progression between levels above "clear" status cost $15,760.03 in 1980 (equivalent to $58,279 in 2023). Scientologists can choose to be audited by a fellow Scientologist rather than by a staff member.

Critics say it is improper to fix a donation for religious service; therefore the activity is non-religious. Scientology points out many classes, exercises and counseling may also be traded for "in kind" or performed cooperatively by students for no cost, and members of its most devoted orders can make use of services without any donations bar that of their time. A central tenet of Scientology is its Doctrine of Exchange, which dictates that each time a person receives something, he or she must give something back. By doing so, a Scientologist maintains "inflow" and "outflow", avoiding spiritual decline.

Starting in 2003 Miscavige began pressuring local Churches of Scientology to purchase larger facilities to use as Scientology centers which would be renovated to become "Ideal Orgs". The theory was "If you build it they will come." This push has included the acquisition of many historic buildings, a plan which professor of religious studies Hugh Urban believes has been pursued to imbue the Church with historical significance and distract from its controversies. For renovations of these buildings, the Church of Scientology has relied heavily on manual labor from Sea Org members in the organization's Rehabilitation Project Force. As of 2018, the Church of Scientology claims it had purchased 70 buildings and opened 60 Ideal Orgs around the globe.

With its membership numbers dwindling, Scientology's ideal org campaign has been called "a real estate scam", a "money-making scam", and "Scientology's principle cash cow". Scientologists were heavily pressured during lengthy fundraising sessions to donate all their money and even open new credit lines to help fund the several million dollar building purchases. This resulted in less money to spend on normal services like training and auditing, so the new orgs became desolate. Staff pay, which is dependent upon weekly org income, was often reduced to a few dollars a week. A 2010 survey of former Scientologists by former Church of Scientology executive Mike Rinder found that the most cited reason for leaving the Church was the unrelenting pressure to donate to programs such as the Ideal Org program.

Some of the buildings purchased for Ideal Orgs remained vacant and unrenovated for years. For example, in the UK, delayed Ideal Orgs included Birmingham (purchased in 2007 and finally opened in 2017), Gateshead (purchased 2007), Manchester (purchased 2006), and Plymouth (purchased 2009). The delays prompted calls from locals for a compulsory purchase of the historically significant buildings, which had remained largely vacant and undeveloped since their purchase.

In order to facilitate the continued expansion of Scientology, the organization has made efforts to win allies in the form of powerful or respected people. Scientology has had a written program governing celebrity recruitment since at least 1955, when L. Ron Hubbard created "Project Celebrity", offering rewards to Scientologists who recruited targeted celebrities, and another church document pointed to the importance of "using Scientology celebrities to mold the opinions of their publics." According to Robert Vaughn Young, "one of my jobs was to get celebrities active, to convince them to hustle and promote Scientology." The Church of Scientology operates Celebrity Centres for the use of artists, politicians, leaders of industry, sports figures, and other prominent individuals.

While some governments now give the Church of Scientology protections and tax relief, other sources describe the organization as a pseudoreligion or a cult. Early official reports in countries such as the United Kingdom (1971), South Africa (1972), Australia (1965) and New Zealand (1969) have yielded unfavorable observations and conclusions. Sociologist Stephen Kent published at a Lutheran convention in Germany that he likes to call it a transnational corporation.

Though it has attained some credibility as a religion in many countries, Scientology has also been described as both a cult and a commercial enterprise. Some of the organization's actions also brought scrutiny from the press and law enforcement. For example, it has been noted to engage in harassment and abuse of civil courts to silence its critics, by identifying as fair game people it perceives as its enemies.

In 1979, several Scientology members were convicted for their involvement in the organization's Operation Snow White, the largest theft of government documents in U.S. history. Scientologists were also convicted of fraud, manslaughter and tampering with witnesses in French cases, malicious libel against lawyer Casey Hill and espionage in Canada.

In his book World Religions in America, religious scholar Jacob Neusner states that Scientology's "high level of visibility" may be perceived as "threatening to established social institutions". The film Going Clear, based on the book by the same name, also documents controversies surrounding the organization and its treatment of former members.

Criticism has also come from within the Church. Marty Rathbun, the former inspector general of the Religious Technology, has spoken out against church activities. He has called for a "Scientology Reformation" to eliminate corruption and bring back the original teachings of L. Ron Hubbard.

From 1952 until 1966, Scientology was administered by an organization called the Hubbard Association of Scientologists (HAS), established in Arizona on September 10, 1952. In 1954, the HAS became the HASI (HAS International). The Church of Scientology was incorporated in California on February 18, 1954, changing its name to "The Church of Scientology of California" (CSC) in 1956. In 1966, Hubbard transferred all HASI assets to CSC, thus gathering Scientology under one tax-exempt roof. In 1967, the IRS stripped all US-based Scientology entities of their tax exemption, declaring the organization's activities were commercial and operated for the benefit of Hubbard. Controversy followed the organization in those years, but its growth continued in the 1960s. New facilities were formed in Paris (1959), Denmark (1968), Sweden (1969), and Germany (1970). In the 1970s the religion spread through Europe: in Austria (1971), Holland (1972), Italy (1978), and Switzerland (1978). Centers of Scientology were in 52 countries by the time the 80s came in and grew to 74 by 1992.

The organization sued and lost repeatedly for 26 years trying to regain its tax-exempt status. The case was eventually settled in 1993, at which time the organization paid $12.5 million to the IRS—greatly less than IRS had initially demanded—and the IRS recognized the organization as a tax-exempt nonprofit organization. In addition, Scientology also dropped more than fifty lawsuits against the IRS when this settlement was reached. Scientology cites its tax exemption as proof the United States government accepts it as a religion. In January 2009, removal of the tax exemption was rated as number 9 in items for the incoming Barack Obama administration to investigate, as determined in an internet poll run by the presidential transition team soliciting public input for the incoming administration. The U.S. State Department has criticized Western European nations for discrimination against Scientologists in its published annual International Religious Freedom report, based on the International Religious Freedom Act of 1998.

In some countries, such as Israel, Scientology is treated legally as a commercial enterprise, and not as a religion or charitable organization. In early 2003, in Germany, The Church of Scientology was granted a tax-exemption for the 10% license fees sent to the US. This exemption, however, is related to a German-American double-taxation agreement, and is unrelated to tax-exemption in the context of charities law. Unlike many well-established religious organizations, Scientology maintains strict control over its names, symbols, religious works and other writings. The word Scientology (and many related terms, including L. Ron Hubbard) is a registered trademark. Religious Technology Center, the owner of the trademarks and copyrights, takes a hard line on people and groups who attempt to use it in ways unaffiliated with the Church of Scientology (see Scientology and the legal system).

L. Ron Hubbard appointed Mary Sue Hubbard to take control of certain aspects of legal protection for the organization in 1968, and the Office of The Guardian was created with its head office situated at Saint Hill Manor. Under The Guardian's Office (later renamed the Office of Special Affairs or OSA), organization members and contracted staff later organized and committed one of the largest penetrations of United States federal agencies ever perpetrated by an organization not affiliated with a foreign government (that is, one such as the KGB). This operation was named Operation Snow White by Hubbard. In the trial which followed the discovery of these activities the prosecution described their actions as such:

The crime committed by these defendants is of a breadth and scope previously unheard of. No building, office, desk, or file was safe from their snooping and prying. No individual or organization was free from their despicable conspiratorial minds. The tools of their trade were miniature transmitters, lock picks, secret codes, forged credentials and any other device they found necessary to carry out their conspiratorial schemes.

The organization has also in the past made use of aggressive tactics in addressing those it sees as trying to suppress them, known as Suppressive Persons (SPs) first outlined by Hubbard as part of a policy called fair game. It was under this policy that Paulette Cooper was targeted for having authored The Scandal of Scientology, a 1970 exposé book about the organization and its founder. This action was known as Operation Freakout. Using blank paper known to have been handled by Cooper, Scientologists forged bomb threats in her name. When fingerprints on them matched hers, the Justice Department began prosecution, which could have sent Cooper to prison for a lengthy term. The organization's plan was discovered at the same time as its Operation Snow White actions were revealed. All charges against Cooper were dismissed, though she had spent more than $20,000 on legal fees for her defense.

On January 22, 2013, attorneys for the organization, as well as some of its members, reacted toward the CNN News Group for its airing of a story covering the release of a book published by a former member, entitled 'Going Clear', published earlier the same year. CNN News Group then chose to publish the reactionary correspondence, with confidential information redacted, on its web site.

According to a 1990 Los Angeles Times article, in the 1980s the Los Angeles branch largely switched from using the organization's members in harassment campaigns to using private investigators, including former and current Los Angeles police officers. The reason seemed to be that this gave the organization a layer of protection.

The Scientology organization has continued to aggressively target people it deems suppressive. In 1998, regarding its announcement that it had hired a private investigator to look into the background of a Boston Herald writer who had written a series on the organization, Robert W. Thornburg, dean of Marsh Chapel at Boston University, said, "No one I know goes so far as to hire outsiders to harass or try to get intimidating data on critics. Scientology is the only crowd that does that." It has apparently continued as recently as 2010. In 2007, when BBC journalist John Sweeney was making Scientology and Me, an investigative report about the organization, he was subjected to harassment:

In LA, the moment our hire car left the airport we realised we were being followed by two cars. In our hotel a weird stranger spent every breakfast listening to us.

Sweeney subsequently made a follow-up documentary, The Secrets of Scientology, in 2010 during which he was followed and filmed on multiple occasions and one of his interviewees was followed back to his home.

The deaths of some Scientologists have brought attention to the organization, both due to the circumstances of their demises and their relationship with Scientology being a factor. In 1995, Lisa McPherson was involved in a minor automobile accident while driving on a Clearwater street. Following the collision, she exited her vehicle, stripped naked and showed further signs of mental instability, as noted by a nearby ambulance crew that subsequently transported her to a nearby hospital. Hospital staff decided that she had not been injured in the accident, but recommended keeping her overnight for observation. Following intervention by fellow Scientologists, McPherson refused psychiatric observation or admission at the hospital and checked herself out against medical advice after a short evaluation.

She was taken to the Fort Harrison Hotel, a Scientology retreat, to receive a treatment sanctioned by the organization called Introspection Rundown. She had previously received the Introspection Rundown in June of that year. She was locked in a room for 17 days, where she died. Her appearance after death was that of someone who had been denied water and food for quite some time, being both underweight and severely dehydrated. Additionally, her skin was covered with over one hundred insect bites, presumably from cockroaches. The state of Florida pursued criminal charges against the Church of Scientology. The organization has repeatedly denied any wrongdoing, and now makes members sign a waiver before Introspection Rundown specifically stating that they (or anyone on their behalf) will not bring any legal action against the organization over injury or death.

These charges attracted press coverage and sparked lawsuits. Eight years later, Elli Perkins, another adherent to Scientology's beliefs regarding psychiatry, was stabbed to death by her mentally disturbed son. Though Elli Perkins's son had begun to show symptoms of schizophrenia as early as 2001, the Perkins family chose not to seek psychiatric help for him and opted instead for alternative remedies sanctioned by Scientology. The death of Elli Perkins at the hands of a disturbed family member, one whose disease could have been treated by methods and medications banned by Scientology, again raised questions in the media about the organization's methods.

In addition, the organization has been implicated in kidnapping members who have recently left the organization. In 2007, Martine Boublil was kidnapped and held for several weeks against her will in Sardinia by four Scientologists. She was found on January 22, 2008, clothed only in a shirt. The room she was imprisoned in contained refuse and an insect infested mattress.

On Friday March 28, 2008, Kaja Bordevich Ballo, daughter of Olav Gunnar Ballo, Norwegian parliament member and vice president of the Norwegian Odelsting, took a Church of Scientology personality test while studying in Nice. Her friends and co-inhabitants claim she was in good spirits and showed no signs of a mental breakdown, but the report from the organization said she was "depressed, irresponsible, hyper-critical and lacking in harmony". A few hours later she committed suicide by jumping from her balcony at her dorm room leaving a note telling her family she was sorry for not "being good for anything". The incident has brought forward heavy criticism of the organization from friends, family and prominent Norwegian politicians. Inga Marte Thorkildsen, parliament member, went as far as to say "Everything points to the Scientology cult having played a direct role in making Kaja choose to take her own life".

Members of the public entering a Scientology center or mission are offered a "free personality test" called the Oxford Capacity Analysis by Scientology literature. The test, despite its name and the claims of Scientology literature, has no connection to Oxford University or any other research body. Scientific research into three test results came to the conclusion that "we are forced to a position of skepticism about the test's status as a reliable psychometric device" and called its scientific value "negligible".

Further recruitment practices — called dissemination in Scientology – include information booths, flyers and advertisement for free seminars and Sunday Services in regular newspapers and magazines, personal contacts, sales of books, and acting classes.

Working with lawyer Bill Drescher, we drafted and implemented one-sided agreements that everyone who partakes in scientology services is required to sign—forfeiting the right to sue and any rights to access the records of scientology services, and even giving scientology authorization to hold the signee against their will should they have a psychotic episode so they can participate in the Introspection Rundown.

— Mike Rinder

Due to previous litigation against the Church of Scientology, and particularly the civil and criminal cases surrounding the death of Lisa McPherson, COS drafted several contracts, releases and waivers which all individuals must sign in order to start any service with COS, no matter how small or introductory. They must be signed again before any major service, and new contracts signed for each Scientology corporate entity the individual visits. One particular waiver—called the "Lisa Clause" by critics of Scientology—states that a member will not seek any psychiatric treatment, and gives permission for the Church of Scientology to detain any member suspected of a psychotic break or other serious mental breakdown. Such detention is to provide the Introspection Rundown, a procedure where an individual is kept isolated from everyone, with no communication. This controversial procedure was considered to be the cause of McPherson's death and, in order to prevent future lawsuits, the Church of Scientology compiled these one-sided contracts.The contracts also prohibit the individual from obtaining any copies of records related to them while granting COS the exclusive right to retain the documents. Individuals waive the right to sue COS in a court of law, and instead they must use Scientology's version of an arbitration (which L. Ron Hubbard never wrote about).

The Church of Scientology denies the legitimacy of any splinter groups and factions outside the official organization, and has tried to prevent independent Scientologists from using officially trademarked Scientology materials. Independent Scientologists, also known collectively as the "Free Zone" are referred to as squirrels within the organization. They are also classified by the Church of Scientology as suppressive persons ("SPs")—opponents or enemies of Scientology. Hubbard himself stated in Ron's Journal '67 "That there were only seven or eight Suppressive Persons on the planet".

In 2010, an exception to the rule was made specifically for the Nation of Islam, which is the only officially sanctioned external Dianetics organization and the first official non-Scientology Dianetics org since 1953. Minister Louis Farrakhan publicly announced his embracement of Dianetics, and has been actively promoting Dianetics, while stating he has not become a Scientologist. He has courted a relationship with the Church of Scientology, and materials and certifications are still required to be purchased from the organization, and are not independently produced.

• List of Scientology organizations – Current and past corporations of Scientology conglomerate
• New religious movement – Religious community or spiritual group of modern origin
• Scientology front groups – Organizations pretending to be not-Scientology
• Scientology officials – Staff hierarchy, practices, personnel of Scientology network

• Lamont, Stewart (1986). Religion Inc.: The Church of Scientology. London: Harrap. ISBN 0-245-54334-1. OCLC 23079677.

• Official website
• Church of Scientology companies grouped at OpenCorporates
• Satellite Image of the Gold Base