Several data sources indicate that female children are regularly subjected to sexual approaches by adult males who are part of their intimate social world. Incestuous families usually appear normal to outsiders; however, incestuous fathers are tyrannical. They often try to isolate their families, restricting both the mobility and the social contacts of their wives and daughters. Most incestuous fathers continue to have sex on demand with their wives as well as their daughters. The incest usually begins when the child is between ages 6 and 12. Daughters often do not tell their mothers about the abuse. Distress symptoms may include insomnia, nightmares, bedwetting, fearfulness, social withdrawal or misbehavior, and somatic complaints. Distress symptoms may heighten as the child reaches adolescence. Many, if not most, incest victims suffer significant and persistent psychological impairment in adult life. Victims have great difficulty with self-esteem and self-protection. Identification is most likely if questions about sexual contacts between adults and children are included routinely in all clinical evaluations. The discovery of incest is a major family crisis requiring fast and decisive intervention. The initial focus should be on stopping the abuse and establishing a safe environment in the family. All family members need intensive support during the crisis period. Family treatment is usually not the most appropriate choice; group treatment for mothers, fathers, and child victims appears much more promising. Self-help programs may also be useful. The child's safety depends on the mother's becoming strong enough to protect herself and her children. The father is ready to return to the family when he has taken full responsibility for the incest. The behavior can be controlled but not cured. Forty-seven references are listed.