The authors describe the case of a man who appeared to have psychotic symptoms, including self-injurious behavior, but who understood his own experience as a religious conversion. The symptoms, clinical course, and treatment response are described with reference to the works of Kurt Schneider and William James. Empirical studies of the attitudes of psychiatrists, psychiatric patients, and clergypersons about the relationship between religious belief and psychiatric illness are described, and various theoretical models used to understand this relationship are articulated.