Rates of sexual activity, pregnancies, and births among adolescents have continued to decline during the past decade to historic lows. Despite these positive trends, many adolescents remain at risk for unintended pregnancy and sexually transmitted infections (STIs). This technical report discusses the new data and trends in adolescent sexual behavior and barrier protection use. Since 2017, STI rates have increased and use of barrier methods, specifically external condom use, has declined among adolescents and young adults. Interventions that increase availability of or accessibility to barrier methods are most efficacious when combined with additional individual, small-group, or community-level activities that include messages about safer sex. Continued research informs public health interventions for adolescents that increase the consistent and correct use of barrier methods and promote dual protection of barrier methods for STI prevention together with other effective methods of contraception.