The description of the problem focuses on varying legal and psychiatric definitions of incest in the United States. Regarding epidemiological findings, the actual incidence of incest is unknown, but recent data suggest incest is not rare and that the majority of perpetrators are male. Major theories of the origin of the incest taboo can be categorized as biological, psychological, familial, and feminist. Evidence to support any of the theories is either lacking or equivocal. Summaries of the characteristics of incest families, perpetrators, mothers, and victims are based in empirical studies. Treatment methods for the perpetrator, victims, and family are described under the categories of family therapy, individual and group insight-oriented therapy, and behavior therapy. The discussion of case management focuses on the disclosure, false accusations, interviewing the child, and evaluating the offender. A separate section of the paper describes a cognitive-behavioral treatment model for the incest perpetrator based on social learning theory. Suggested research is designed to obtain basic knowledge regarding incest, followed by more sophisticated research designed to assess the contributions of specific treatment components. Research on incest prevention is also recommended. 66 references.