Depression in childhood and adolescence has become a topic of considerable research interest in the last decade. A number of studies ranging over the last half-century provide information about the prevalence of depressive symptoms and syndromes in non-referred populations. These studies are critically reviewed in the light of an analysis of the various meanings that the term 'depression' may carry, and a variety of methodological issues. The sparse evidence for the involvement of a number of potential risk factors for depressive disorders is then considered and suggestions for future work in this area are outlined.