OBJECTIVE To examine how cohort trends in family, individual, and relationship characteristics are linked to trends in adolescent reproductive health outcomes to provide a better understanding of factors behind recent declines in teenage birth rates. METHODS We examine a sample of three cohorts of females and males aged 15-19 in 1992, 1997, and 2002, based on retrospective information from the 2002 National Survey of Family Growth. We identify how family, individual, and relationship characteristics are associated with the transition to sexual intercourse, contraceptive use at first sex, and the transition to a teen birth. RESULTS Cohort trends and multivariate analyses indicate changes in family and relationship characteristics among American teens have been associated with positive trends in reproductive health since the early 1990s. Factors associated with improvement in adolescent reproductive health include positive changes in family environments (including increases in parental education and a reduced likelihood of being born to a teen mother) and positive trends in sexual relationships (including an increasing age at first sex and reductions in older partners). These positive trends may be offset, in part, by negative changes in family environments (including an increased likelihood of being born to unmarried parents) and the changing racial/ethnic composition of the teen population. CONCLUSIONS Recent increases in the U.S. teen birth rate highlight the continued importance of improving reproductive health outcomes. Our research suggests that it is important for programs to take into consideration how family, individual, and relationship environments influence decision-making about sex, contraception, and childbearing.