Legally and socially, incest is viewed as sexual and social deviancy. Further, the perpetrator's deviance may contribute to sexual evidence in the victim. Reported incest rates are highest among the lower classes, but other studies note that incest is found in all social classes. While there is disagreement with respect to validity of risk factors and the characteristics of victims, perpetrators, and colluding parents, certain findings have been consistently reported. The victim is usually a female under 17 years old, the perpetrator is generally the biological father, the incest usually is protracted and begins before the child reaches puberty, and incest usually occurs in intact families. In addition, extreme paternal dominance, paternal alcoholism, paternal authoritarianism, an indifferent or intimidated mother, marital sexual problems, social isolation, and role disorganization in the family appear to be contributory factors. Short-term effects on the victim are primarily emotional in many cases, but long-term effects may include dysfunctional sexual and interpersonal relationships. Treatment has included individual and family approaches and self-help groups. Preventive efforts have focused on identifying high-risk families and education. Much research suffers from methodological problems (small samples, inadequate measurement, lack of rigorous program evaluation) which should be remedied in future research. 3 footnotes and 80 references.