The aim of this study was to assess the knowledge of men who have sex with men (MSM) about STDs and the sources, reliability and accuracy of that knowledge, furthermore, to determine the frequency of hepatitis B, hepatitis C, syphilis and HIV infections. A questionnaire was prepared to know socio-demographic characteristics, their medical situation, and knowledge about prevention from STDs. Blood samples were obtained for serological tests. Ninety four MSM filled the questionnaire and also, 39 of them were screened to STDs. Mean age was 23.3 ± 4.6 years. High school or university graduates were 72.6% and 29.4% did not have a health insurance. Cigarette, alcohol, heroin and cocaine usage were 62.8%, 46.8%, 10.6% and 1.1% respectively. In the last year, 23.4% had multiple sexual partners. Majority of subjects were aware of transmission of HIV/AIDS by sexual intercourse (88.3%) and blood or blood products (77.7%). Subjects with 69.1% had history of unprotected sex. Major source of their awareness was from internet or other media. One of them was anti-HIV positive. An education program was commenced in small groups.\nThis is a basic study on homosexual groups, summarizing their problem and risks in Kayseri at the Center of Turkey.