Modern cults and zealous self-help movements exercise an intense group influence and can have a major impact on their members' psychiatric status. On the basis of research findings, the author describes the charismatic group, a generic model for such cohesive, intensely ideological movements. He examines the psychological forces they tap and the way they can both relieve and exacerbate psychopathology. The model is then used to explain the operation of zealous self-help programs that address psychiatric syndromes; these are directed at problems of the medically ill, substance abusers, and relatives of psychiatric patients.