The consequences of childbearing for adolescent parents, their children, and society are severe. We have focused exclusively on one consequence of adolescent sexual activity, namely, pregnancy. In so doing we are not denying the presence of other serious consequences of sexual activity, including sexually transmitted diseases, particularly the acquired immunodeficiency syndrome. For almost all young people, pregnancy should be prevented or at least delayed. Prevention is difficult, however, because it involves understanding the complexities of adolescence as a stage in the development of the individual. It also requires increased understanding of the behavioral and cultural origins of adolescent sexual activity and pregnancy. Physicians are among those with a reasonable understanding of the individual and societal factors that influence the sexual activity of adolescents. Because of their contacts with patients and families, including adolescents, they are in a pivotal position to recognize early sexual activity, to counsel young people about ways to prevent pregnancy, and to prescribe contraceptives when appropriate. Physicians should consider taking leadership positions in the community in both educational efforts and preventive services. In some communities, physicians work closely with educators in developing and teaching family life programs in the schools. They also are in influential positions to improve the availability of preventive contraceptive services through development of community-based services. The Robert Wood Johnson High-Risk Youth Programs are an excellent example of the types of community-based services that should be provided for adolescents. Physicians can serve as an educational resource about a wide spectrum of health issues for young persons and their families and communities.(ABSTRACT TRUNCATED AT 250 WORDS)