The Church of Scientology has claimed to have as many as 10 million members as of 2006,though actual membership figures it has released indicate a far smaller total. Third party estimates of Scientology's worldwide membership range from less than 100,000 to approximately 500,000. According to a 2001 survey published by the City University of New York, 55,000 people in the United States would, if asked to identify their religion, have said Scientology.
The first Church of Scientology was incorporated in Camden, New Jersey as a non-profit organization in 1953. The Church forms the centre of a complex worldwide network of corporations dedicated to the promotion of L. Ron Hubbard's philosophies in all areas of life. This includes:

- Drug treatment centres (Narconon);
- Criminal rehabilitation programs (Criminon);
- Activities to reform the field of mental health (Citizens Commission on Human Rights);
- Projects to implement Hubbard's educational methods in schools (Applied Scholastics);
- A "moral values" campaign (The Way to Happiness);
- A political action committee, (Citizens for Social Reform) to promote social programs with legislators at the US federal and state levels;
- World Institute of Scientology Enterprises, or WISE, which licenses Hubbard's management techniques for use in businesses;
- A consulting firm based on Hubbard's management techniques (Sterling Management Systems);
- A campaign directed to world leaders, as well as the general public, to implement the 1948 United Nations document "The - Universal Declaration of Human Rights" (with particular emphasis on the religious freedom elements).
Within the church, members are arranged in a hierarchically pyramid ranked structure, with higher level members holding authority over lower ranked subordinates, especially as evidenced by the Sea Org.