Peer education remains a popular strategy for health promotion and prevention, but evidence of its effectiveness is still limited. This article presents a systematic review of peer education interventions in the European Union that were published between January 1999 and May 2010. The objective of the review is to determine the effectiveness of peer education programs for human immunodeficiency virus (HIV) prevention, adolescent pregnancy prevention and promotion of sexual health among young people. Standardized methods of searching and data extraction were utilized and five studies were identified. Although a few statistically significant and non-significant changes were observed in the studies, it is concluded that, overall, when compared to standard practice or no intervention, there is no clear evidence of the effectiveness of peer education concerning HIV prevention, adolescent pregnancy prevention and sexual health promotion for young people in the member countries of the European Union. Further research is needed to determine factors that contribute to program effectiveness.