The main objective of this review is to answer the following research questions: What are the effects of outreach programmes on problem/high-risk behaviour of young people between 8 and 25 years of age living in OECD countries? Are they less likely to experience an adverse outcome such as school failure or drop-out, runaway and homelessness, substance and/or alcohol abuse, unemployment, long-term poverty, delinquency and more serious criminal behaviour? The proposed project will follow standard procedures for conducting systematic reviews using meta-analysis techniques. In order to summarise what is known about the possible causal effects of outreach, all study designs will be included that use a well-defined control group. Nonrandomised studies, where outreach has occurred in the course of usual decisions outside the researcher's control, must demonstrate pretreatment group equivalence via matching, statistical controls or evidence of equivalence on key risk variables and participant characteristics. These factors will be outlined in the protocol, and the methodological appropriateness of the included studies will be assessed according to a risk of bias model.