The States are forbidden to restrict religious freedom under the first and fourteenth Amendments. Where infringement is caused by State employees, such as prison officials, rather than legislation, prisoners may sue under the Civil Rights Act of 1871, U.S. Statute 1983. Moreover, the New York Correction Law gives prisoners the right to free exercise of religion, subject to the disciplinary needs of the prison. Prisoners may bring action in State and Federal court simultaneously against prison officials restricting religious freedom. A discussion of rights under present law covers the right to believe, State and Federal court definitions of religion, and the means to and importance of demonstrating religious sincerity in court. A discussion of religious services in prison points out that corrections officials in New York must issue regulations protecting the exercise of religion and may not restrict visitation to clergymen of approved denominations. Moreover, prisons are severely restricted in censoring religious mail. A discussion of the conflict between free exercise of religious expression and the need for proper prison management reveals that courts usually balance the importance of a religious practice with prison needs, allowing interference only if a practice causes substantial problems. Moreover, case rulings show that prisons may not restrict a religious practice in the interest of discipline if another means exists to achieve the same end. However, the courts will accommodate religious dietary requirements only where it is reasonable, practical, and consistent with prison resources. Finally, although a clear test for the constitutionality of a prison restriction on religion does not exist, a suggestion is made on how to develop such a test. Footnotes are included.