During the 1980s, an increasing proportion of adolescent women reported having had premarital sexual intercourse, thus potentially placing an increasing number of young persons at higher risk of acquiring a sexually transmitted infection. To determine rates and examine trends of sexually transmitted infections among adolescents, we analyzed data for reported cases of gonorrhea and primary and secondary syphilis among 10- to 19-year-olds for 1981 through 1991. Summary data for cases of gonorrhea and primary and secondary syphilis that were identified and reported to state health departments were sent annually to CDC. These data included total number of cases by disease (gonorrhea, primary and secondary syphilis), sex, racial/ethnic group (white, not of Hispanic origin; black, not of Hispanic origin; Hispanic; Asian/Pacific Islander; or American Indian/Alaskan Native), 5-year age group, and source of report (public, private). From 1981 through 1991, 24%-30% of the reported morbidity from gonorrhea and 10%-12% of the reported morbidity from primary and secondary syphilis in the United States affected the adolescent age groups. Some of the highest rates of gonorrhea during that time period were among 15- to 19-year-olds. Gonorrhea rates among adolescents increased or remained unchanged from 1981 through 1991, while the rates among older age groups decreased. Although primary and secondary syphilis rates were lower among adolescents than older age groups, adolescents contributed to the epidemic of syphilis that occurred from 1987 through 1990. Differences in reported rates of both syphilis and gonorrhea among white, black, and Hispanic adolescents increased during the latter half of the 1980s. Reporting biases could account for some the differences among rates for white, black, and Hispanic adolescents. However, if gonorrhea has been underreported for any racial group, the high rates of gonorrhea among 15- to 19-year-olds represented an underestimate of the true infection rate. Increases in sexual activity among adolescents and a lack of clinical services in settings convenient to adolescents could have contributed to the increasing rates of gonorrhea and syphilis among these young persons during this time period. If gonorrhea and other sexually transmitted infections are cofactors for facilitating the transmission of human immunodeficiency virus (HIV), the high incidence of gonorrhea in some locales among some populations of adolescents could result in dramatic increases in HIV acquisition, a situation that demands attention from public health organizations.