This paper describes some of the complex difficulties faced by therapists treating incestuous families. The many levels of transference and countertransference are described, pointing to one reason for treatment complexity. It is claimed that the therapist's emotional reactions can be understood as a parallel to the internal and interpersonal dynamics in the family, and utilized as a tool in treatment. Specific countertransference difficulties which are addressed include feelings of hate towards the incest perpetrator, discomfort in discussing sexuality, victim/victimizer patterns, and boundary violations in treatment. The histories of sexual abuse of the perpetrator and the spouse in incestuous families is reviewed. Therapeutic boundaries are described. Case presentations are utilized to illustrate these ideas. Literature on relevant topics is cited. It is noted that whatever form countertransference takes, it is essential that the family therapist be able to use the feelings to understand parallel experiences in the family as a whole and in the individual members' internal worlds and that feeling perplexed in treatment is often a necessary step for the therapist in digesting the experience in order to use it therapeutically. It is concluded that only when therapists are able to tolerate the difficult feelings can they expect the incestuous family to have the courage to set out on its own painful journey toward change. (Contains 19 references.) (Author/ABL)