Data collected over a two-year period from more than 500 teenagers and their mothers indicate that neither parental attitudes toward premarital sex nor parent-child communication about sex and contraception appear to affect teenagers' subsequent sexual and contraceptive behavior. Teenagers are often ignorant of their parents' attitudes toward sex-related issues, and they and their parents often contradict one another in describing the kinds of sex-related conversations they have had. In only two cases was a significant relationship found between communication and adolescent behavior: Girls whose mothers reported that they had discussed sex with their daughters were less likely to subsequently initiate coitus; and girls who reported that their mothers had discussed birth control with them were more likely to use effective contraceptives. However, the former association disappeared when it was the daughters who reported the communication, and the latter disappeared when it was the mothers who reported it.