This guide to therapeutic treatment of incest is based on the Multiple Systems model, the underlying assumption of which is that every family has a degree of vulnerability arising from four factors: environmental or sociocultural perspectives, family-of-origin or the influence the parents' families had on their views of marriage and childrearing, individual personality and psychopathology, and family systems including interactions and communications styles of family members. If there is a precipitating event (such as drug or alcohol use, acute stress, or a unique opportunity) and the family's coping skills (including social networks, strong religious beliefs, and the use of therapy or self-help groups) are inadequate, incest can occur. The Multiple Systems Model is advantageous over the perpetrator-victim and family systems models because its complexity increases the number of clinical options and allows for processing more varied information, it encourages treatment where it is needed, it has practical meaning in terms of the cause of the incest, and it can be used by therapists from differing clinical-political orientations. 1 appendix, 179 references.