This survey produced baseline information about student knowledge of sexually transmitted diseases (STDs), their sexual attitudes, and their behavior to help establish control and education programs. The study was conducted at Ege University, Izmir, Turkey, during the 1999-2000 academic year. A total of 2,217 first- and fourth-year students determined by stratified sampling constituted the study group. All students who volunteered to participate completed a questionnaire assessing sociodemographic and knowledge factors, sexual attitudes, behavior, and history of STDs. The rate of students having had sexual experience was 36.6%. Males were more sexually active than females. Most students (71.4%) began sexual activity at ages 15-19 without any difference by gender. Males reported significantly more sexual partners than females. Similarly, the rate of male students never using condoms was significantly higher than females. Condom was the most frequent contraception method, followed by oral contraceptives and withdrawal. Mean score on the knowledge questions was 16.29 (highest score 30). The most widely known STD was HIV infection and AIDS. Students' knowledge of transmission routes, signs and symptoms, and risk groups of STDs was insufficient. Main sources of knowledge were visual and print media, and friends. Most students (84.7%) viewed prevention from STDs as a person's own responsibility. Young people in Turkey are sexually active and tend to engage in high-risk behavior. However, their knowledge on sexual health and sexually transmitted diseases is insufficient. Study results suggest a need for implementation of STD control programs and provision of school sexuality education for adolescents and young adults.