The surface action of a family system, its patterns of communication, alliance, parenting, atmosphere, and relationships with the outside world, provides psychological support to all members and nurturance and socialization for children. The surface action in an incestuous family does not meet these needs in an appropriate way relative to the maturity of the family members, and sexualization of nurturant physical contact is substituted, which in itself becomes a problem. The boundaries and roles within an incestuous family have become confused, the parenting coalition has failed, and rapid role reversals are common. Dysfunctional families may employ incest to maintain their own integrity and existence by helping members avoid painful realities and perpetuating a body of myths that are repeatedly confirmed by family consensus over the years. A feedback circularity within the incestuous family is established which results in a homeostatic system that keeps all disagreements within the family. Thus, stopping the sexual abuse is not enough, and the underlying family dynamics must be addressed. If someone outside the family knows about the incest, then someone within the family is uncomfortable with the incestuous behavior. The intervener must give relief to the initial complainer, working against the family attacking him or her. The therapist also must be active, almost intrusive, and determined to participate in the tight, incestuous family system in order to modify it. Family treatment does not necessitate seeing all the family at every session, but the therapist can work with individual members and dyads for specific purposes. A case study demonstrates the systems approach to evaluating an incestuous family and intervention methods. The paper includes 21 references.