This article presents the results of three studies as they relate to the influence of the family on adolescents' sex lives. The first study examined sexual and contraceptive practices among girls aged 12-19 in Mexico City. It was found that both communication with the mother and pregnancy history of close female relatives were predictors of initiation of sexual relations, contraceptive use, and pregnancy. The second study examined differences between young men who had gotten their partner pregnant and young men who had not. Again, communication levels with parents were found to influence behavior. The final study examined levels of communication about sex as perceived by parents and their children. Mothers had higher levels of communication with their children about sex than did fathers, and fathers' perception of what they were communicating differed substantially from their children's perception. As a whole, the three studies' results support the hypothesis that the family has a substantial influence on adolescents' sexual and contraceptive behavior and provides justification for the incorporation of such issues as parent-child communication into sex education programs.