The purpose of this study is twofold: to evaluate the extent of knowledge possessed by young people residing in an urban sexually transmitted disease (STD) and AIDS epicenter about STDs, including AIDS; and to determine whether knowledge levels varied by age, gender, race/ ethnicity, and/or previous health instruction. A total of 867 adolescents (472 females and 395 males) attending a large public high school in New York City completed a self-administered survey. Levels of knowledge about AIDS transmission and prevention were high (mean percentage correct = 91.8%). Nonetheless, adolescent respondents locked awareness about the prevalence of common STDs, had limited understanding of the ways in which these diseases can be transmitted and prevented, and were unaware of potentially serious sequelae resulting from exposure to infectious agents (e.g., infertility from chlamydial infections). Young people who had taken a health education course in which STDs were discussed did slightly better on the knowledge survey than did their peers. While the prevention of HIV infection is, and should be, a national priority, more concerted efforts are needed to better educate young people about other STDs in the overall context of sexual health.