Across various studies, women were twice as likely to be depressed compared with men. The literature on adolescent depression is much more inconsistent concerning gender differences. The goals of this study were to identify the age at which the gender gap in depression commonly identified among adults began to manifest; to assess the ability to generalize this phenomenon across populations; and to assess the robustness of this divergence using a variety of instruments. The two-wave, 1994-1996 Canadian National Population Health Survey used a diagnostic measure across a 24-month interval, providing 12-month prevalence rates of major depressive disorder. The British Youth Panel measured depressive symptomatology across five annual waves beginning in 1995. The two-wave 1995-1996 National Longitudinal Study of Adolescent Health used a measure of depressive symptomatology across a 12-month interval. Results showed the commonly observed gender gap between males and females across all waves for each survey regardless of which measure was used. The gender gap consistently emerged in early adolescence across all three samples. This analysis identified differences in depression between males and females emerging by age 14. The emergence of this gender gap is captured by both diagnostic instruments and categorical cutpoints of depression scales, consistent with studies of adult depression. The study of the emergence of gender differences in depression is an important area of inquiry for assisting clinicians in the prevention, recognition, and treatment of adolescent-onset depression. 3 figures, 1 table, 47 references