As part of a larger study on the impact of personal and family characteristics on adolescents' HIV risk and risk-reduction behavior, 90 adolescents and 73 mothers were asked to define in their own words seven terms related to sexual development: ejaculation, hormones, menstruation, ovulation, puberty, semen, and wet dreams. Mother and adolescent knowledge of sexual development terms and the effects of age and sexual experience on that knowledge were examined. Results suggest that the mothers were not able to adequately define the sexual development terms and thus may be ill-prepared to teach their children about sex or reinforce information they learn in school. Since adolescent knowledge did not significantly increase with age and sexual experience, the researchers suggest that continuing sex education about normal sexual development is needed.