Adolescence is a transition period between childhood and adulthood in which physical, sexual and psychosocial changes occur. Sexually Transmitted Infections (STI) are the most common reproductive health problems adolescents face. Peer education is a very useful method in adolescents' education, especially on risk factors and risk taking behaviors. This peer education intervention study, including two base line studies (one before and one after the intervention), was conducted in four classes of an Anatolian high school in Ankara in 2000. The aim of the study was to evaluate the success of the peer education model. There was a significant difference in the general scores of the students before (29.52; SD = 4.38) and after (31.89; SD = 4.96) education by peer educators (p = 0.000). This study might have assisted the study population in establishing safe sex practices for a healthy sexual future.