The subjects were 561 paraphiliacs recruited through informal and formal discussions with health professionals and criminal justice sources and through newspaper advertisements. Extensive precautions were taken to protect the subjects' confidentiality and to ensure full reporting of their sexually deviant acts. Structured clinical interviews gathered information on demographic characteristics, the frequency and variety of deviant sexual acts, and the number and characteristics of victims. The subjects ranged from 13 to 76 years in age and averaged 31.5 years. They had varied religious orientations. The subjects completed a total of 291,737 paraphilic acts. The numbers of acts ranged from an average of 7.2 rapes committed by those involved in rape to 1,139.2 acts completed by paraphilics involved in masochism. The majority of child molestations were committed by individuals who targeted young boys outside the home, followed by incest with a female family member. An earlier report that convicted pedophiles had been found guilty of fewer than 3 paraphilic acts per offender contrasted sharply with this study's finding of from 23.2 to 281.7 acts per offender. The infrequency of rape relative to child molestation also contrasts with media portrayals of these subjects. The findings showed the possibility of gaining the cooperation of sex offenders in research studies through the use of appropriate precautions. Data tables and 30 references.