One out of every 10 women aged 15-19 becomes pregnant each year in the United States. Of these pregnancies, five out of every six are unintended--92 percent of those conceived premaritally, and half of those conceived in marriage. The teenage pregnancy rate is high because only a minority (one in three) of sexually active young women always use contraceptives, and only one in two of these women rely on the most effective methods. The two most common reasons given by adolescents for not using contraceptives are believing that the risk of pregnancy is small, and failing to anticipate intercourse. Experience in other developed countries clearly shows that the incidence of adolescent pregnancy can be reduced if effective contraceptives are made widely available. Although high quality sex education programs that include information about contraception, reproductive biology and responsible sexual behavior can enhance the effectiveness of contraceptive delivery systems, they are not a substitute for the actual provision of services and supplies. However, there is formidable political opposition to the provision of such services by a vocal minority who believe that the crux of the problem is premarital sexual activity, and that lowering the cost of such behavior by reducing the risk of pregnancy will both legitimize adolescent sex and increase its prevalence. Consequently, there is a political impasse that guarantees a continuing large number of adolescent pregnancies. Further, even if contraceptives and sex education were readily available to all adolescents, there would still be a pool of teenagers who would see little benefit in postponing parenthood. This pool would be composed overwhelmingly of the poor and of blacks and Hispanics. Increasing the demand for pregnancy prevention among young women and men in this hard-core, high-risk group will be extremely hard to achieve without a fundamental restructuring of society.