Literature indicates that overt incest occurs in every civilized country at the rate of approximately one case yearly per one million persons. Sibling relationships are probably most common, but father-daughter relationships constitute the majority of reported cases. Incest is not (as was once thought) a lower-class phenomenon associated with poverty, inadequate housing, and low moral standards. Incestuous relationships typically involve collusion by all family members. The incestuous father, who is usually around age 40, incest with his oldest daughter, whose age may range from 6 to adulthood; he subsequently engages other daughters. Although the incest-prone father may be influenced by the loss of a wife, father-daughter incest usually takes place in an unbroken home and begins following sexual estrangement between husband and wife. Liaisons tend to be protracted and are terminated only upon intervention of authorities. Incestuous fathers have frequently suffered parental separation or death and lack of understanding in their developmental years. Their incestuous behavior is usually not associated with general criminal tendencies or with any particular psychological disturbance, although incestuous fathers are frequently immature in their sexual orientation and are capable of extreme rationalization. The wives of incestuous fathers tend to be dependent, infantile women who foist responsibility on their daughters prematurely, frustrate their husbands sexually, encourage father-daughter intimacy, and tolerate or deny the liaisons. Incestuous daughters are precocious in learning and reality mastery, eager to assume adult roles, and gratified by their fathers' attention. The daughters rarely resist or feel guilt and frequently become promiscuous following incest. Later psychological disturbances from incest participation are not apparent. Generalizations about mother-son incest, sibling incest, or homosexual incest are difficult because of inadequate data. However, absence of the father appears to contribute to mother-son incest, and lack of parental supervision contributes to sibling incest. Incestuous temptation would appear to derive from unique combinations of certain needs and attitudes of family members. Seventy-four references are supplied.