The behavioral, criminological, and legal aspects of incest in the United States are explored, and ambiguities of legal definitions and the lack of uniformity among States in prosecuting offenders are noted. Accurate statistics on the incidence of this offense are not available. Available data are chiefly projections of known cases, complaints, and prosecutions. Father-daughter incestuous relationships appear to be the most frequent type of incest occurring in the United States. The behavior is known to cause harmful, long lasting effects on the victims, who have a tendency to become emotionally disturbed, deviant women who are incapable of normal sexual interaction within a loving man-woman relationship. The incestuous father is often an apparently normal, law abiding citizen; his wife frequently allows or even encourages the incestuous relationship. One of the few incest intervention programs in this country, the Child Sexual Abuse Treatment Center in Santa Clara County, California, features a multifaceted approach based on humanist psychology, Gestalt theory, and the psychosynthesis theory to foster positive family interaction and to reduce the emotional impact of incest upon all parties involved. A total of 39 references are appended.