Explanations for the occurrence of incest can be grouped into four general categories. Although some authors and clinicians have stated that one category of explanations best explains incest, the literature contains empirical and case report support for each category. In this article, it is argued that each category of explanations is useful for understanding incest, and that a single category can explain only a small minority of incest cases. Most cases are more effectively characterized by a combination of explanations. Assessing which of the explanations describes a particular incestuous family will provide valuable guidelines for determining the most appropriate legal and therapeutic interventions for that family.