Peer education is used as a health promotion strategy in a number of areas, including sexual health. Although peer education programmes have been around for some time, published systematic evaluations of youth sexual health peer education programmes are rare. This article discusses the advantages and disadvantages of youth sexual health peer education programmes, the importance of programme evaluation, and strategies for developing effective programme evaluation tools. The value of conducting both process (programme delivery) and outcome (programme impact) evaluation is examined as well as methods for conducting these forms of assessment. Considering the wide range of peer education programmes and the diversity of communities served, the article concludes that the creation of a single evaluation method may be an impossible task. To address this challenge, principles for effective programme evaluation are proposed with tools that can be tailored to the unique goals of specific sexual health organizations.