To increase understanding of sexual abuse in boys, we reviewed records of 142 victimized boys ranging in age from 6 months to 17 years. They represented 14% of victims under 18 years of age during a four-year period. Most had histories of single assaults (87%) that involved attempted anal intercourse (78%) by know assailants (59%). Half of the assaults were violent, with evidence of trauma found in 24%. Patterns of abuse were associated with the victim's age and the assailant-victim relationship. Younger victims reported more non-stranger assaults, less violence, and less anal intercourse. Assaults by strangers tended to involve older children and more violence and to occur away from home. Male children are at significant risk of sexual abuse, often at younger ages than girls. Consequences of sexual abuse remain unknown, but may relate to future child abuse.