PIP: This discussion of the sexually active teenager provides a statistical analysis of sexual behaviors and reviews developmental issues, contraceptive usage, adolescent pregnancy and its associated problems, and sex education. Major changes have occurred over the past 2 decades in sexual mores, contraceptive technology, the acceptance of single parent families, and the availability of induced abortion. In the US adolescent pregnancy and epidemic venereal disease have become major child health problems. It is important that the pediatrician, family practitioner, nurse practitioner, and mental health professional are aware of the magnitude of these problems and their potential areas for intervention. Various epidemiological studies of sexual behavior have documented an increase in the number of sexually active adolescents over the last decade. In a survey of metropolitan adolescents, Zelnik and Kantner found that the reported sexual activity among 15-19 years old adolescent girls increased from 30% in 1971 to 50% in 1979. Among never married white teenagers in this age group, statistics from 1971 indicated that 23% were sexually experienced, and this incidence increased to 42% in 1979. Much less is known about the sexual behavior of younger adolesents in the 11-14 year old range. The increased number of adolescents involved in premarital intercourse, coupled with the earlier age of menarche and delayed marriage, has increased the risk of premarital pregnancies. The number of adolescents between ages 15-19 experiencing a premarital pregnancy has increased significantly from 8.5% in 1971 to 16.2% in 1979, the most notable increase occurring among white teenagers. Among sexually experienced 15-19 years olds, 32.5% have experienced a premarital pregnancy. Sexual behavior among young adolescents is influenced by several variables, including maturation, personal values about premarital sex, inclination, and opportunity. There is an increasing tendency for adolescents to view sexual behavior as a matter of personal choice rather than a morality issue. Adolescents in all stages of development may delay obtaining adequate contraception. Denial of fertility is a common theme in early as well as late adolescence. The consistency and responsibility required for effective contraceptive use is not always compatible with the stage of adolescent development in which they have chosen to become sexually active. Use of effective contraception is often related to increasing sexual activity, increasing closeness of a relationship, a pregnancy scare because of a late or missing period, the positive influence of friends and family members or physicians, and/or the actual discovery of a contraceptive program. For adolescents access to contraceptives has been problematic and prescription contraception is frequently discontinued with continued sexual activity. Feelings of despair, worthlessness, and chronic school failure appear to be common factors among adolescents who choose to carry a pregnancy to term. Sex education courses should facilitate decision making about responsible sexual behavior.