This study reviews research examining the incidence of incest and child sexual abuse, focusing on the apparent discrepancy between incidence rates based on child service agency incident reports and the surveys of victims reports. Research is reviewed from the 1950s, 1970s, and 1980s. Research problems and limitations are described. The problem with varying definitions of incest and sexual abuse is discussed. Age-related reasons for underreporting of abuse are discussed, noting that younger children do not understand the notion of aberrant sexuality or its consequences. Positive and negative consequences of child sexual abuse reported in the literature are reviewed. Recent literature focusing on the initial or proximate effects of incest and sexual child abuse is described. The literature review presents these conclusions: (1) the seriousness of the problem of incest and sexual abuse is difficult to determine because of the discrepancy between official reports or incidence versus what has been found in recent victimization survey studies; (2) much of the discrepancy is due to lack of a standardized definition of sexual abuse; (3) there is an unknown degree of underreporting of sexual abuse made to child service agencies. (Author/ABL)