Most literature references cite brother-sister incest; some research indicates that girls are as likely to take part in sibling incest as in parent-child incest. Reasons for sibling incest may include sexual experimentation, situational pressures, personality disorders, problems in the family system, and inappropriate roles within the family system. Sometimes two willing partners are involved; in other cases, one party is the aggressor. In assessing whether the behavior is harmless curiosity or potentially detrimental, it is important to determine what is normal sexual behavior, nature and duration of the incest, the way it occurs, the age of the siblings, and the family dynamics. Case management must focus on the child and the family, denial of the impact of the incest, potentially damaging responses among family members, the need for an appropriate initial contact, and the need to deal with the underlying problem of which incest is a symptom. The therapist must have persistence and flexibility and be willing to confront family resistance. Family members must be assured of privacy and confidentiality. The therapist must also focus on the impact of the family, society, and the environment on the client. Fifteen references are listed.