The aim of this study was to determine the level of knowledge about sexually transmitted diseases and the frequency of behavior presenting risk for acquiring those diseases among students of Medical colleges in relation to gender. The study is based on a cross-sectional survey conducted in two Medical colleges in Belgrade in December 2016. A total of 670 students (96%) completed an epidemiological questionnaire. Respondents were selected through random sampling, they took part in the study voluntarily and filled in the questionnaire anonymously and independently. The questionnaire included 18 questions on demographic characteristics, knowledge and risky behavior. Female students were significantly older than male students (p= 0.014). Male students were more often single, while female students were mostly in the relationship or married (p< 0.001). Female students have more knowledge about symptoms of sexually transmitted diseases (p= 0.008) and more than males are familiar with the causality of HPV infection and cervical cancer (p= 0.002). Males students earlier had the first sexual intercourse (p< 0.001), had sex on the first date (p< 0.001), changed sexual partners during their lives (p< 0.001), and paid for sex (p< 0.001). Male students have specific risk factors for unhealthy sexual behavior. It is necessary to upgrade the education programs and implement population-targeted prevention and control measures for sexually transmitted infections