This paper quantitatively reviews longitudinal studies examining three central cognitive theories of depression--Beck's theory, Hopelessness theory, and the Response Styles theory--among children (age 8-12) and adolescents (age 13-19). We examine the effect sizes in 20 longitudinal studies, which investigated the relation between the cognitive vulnerability-stress interaction and its association with prospective elevations in depression after controlling for initial levels of depressive symptoms. The results of this review suggest that across theories there is a small relation between the vulnerability-stress interaction and elevations in depression among children (pr = 0.15) and a moderately larger effect (pr = 0.22) among adolescents. Despite these important findings, understanding their implications has been obscured by critical methodological, statistical, and theoretical limitations that bear on cognitive theories of depression. The evidence base has been limited by poor measurement of cognitive vulnerabilities and over reliance on null hypothesis significance testing; these have contributed to a field with many gaps and inconsistencies. The relative paucity of research on developmental applications of such theories reveals that surprisingly little is known about their hypothesized etiologic mechanisms in children and adolescents. Ways to advance knowledge in the area of cognitive theories of depression among youth are discussed.