Peer education is increasingly being used to increase HIV and AIDS awareness among youth. This pilot cohort study tested the effectiveness of this approach among high school students in 10 schools in Athens, Greece. Over one year, 702 students were followed (n = 493 experimental group, n = 209 control group) and knowledge, attitudes, behaviors, and practices assessed through a pre and post intervention questionnaire. Students in the intervention group were moderately more empowered to take personal responsibility and adopt safer sexual practices. Noámodification in knowledge was observed between the two groups. This type of education did not appear to influence discrimination against certain groups of people, condom use and initiation of sexual relations.