Based on reported prevalence rates of 3 percent to 31 percent, the current best guess suggests that contact abuse occurs in 2 to 5 percent of the male population. Retrospective community evidence reveals that one boy is abused for every two to four girls abused, while the highest clinical ratios are one boy to every four girls. Major explanations for the apparent underreporting or underdetection of male sexual abuse have been the boys' fears of disbelief and of being labeled homosexual. The recent development of aggressive behavior, homophobic anxiety, and abuse of a sibling as well as abusing behavior are possible indicators that a boy has been sexually abused. Other research findings are that boys are more frequently subjected to anal abuse than girls, that the initial effects of abuse are more harmful to boys than to girls, and that men experience adverse longer-term effects similar to those in women. However, little is known about treatment effectiveness and outcomes in sexually abused boys. Nevertheless, all future research on child sexual abuse should include gender analysis. Tables and 200 references