This study examined whether instruction in school and at home about how to prevent victimization has any impact on children's behavior in situations of real victimization threat. Telephone interviews were conducted in 1992 with a nationally representative sample of 2,000 youths age 10 to 16 and their caretakers. More comprehensive school programs had mixed, small but overall positive effects. Children exposed to such school-based prevention programs performed better on a short test of knowledge about sexual victimization; when victimized or threatened were more likely to use the self-protection strategies recommended by prevention educators; were more likely to feel that they had been successful in protecting themselves; and were more likely to disclose to someone about the victimization attempts. They were not better able to limit the seriousness of the assaults and, in fact, they experienced more injuries in the course of sexual assaults. Comprehensive parental instruction also had positive effects on knowledge, the use of preferred self-protection strategies and the likelihood of disclosure. Children with comprehensive parental instruction were more likely to limit the seriousness of assaults.