Data were collected on the point and lifetime prevalences, 1-year incidence, and comorbidity of depression with other disorders (Diagnostic and Statistical Manual of Mental Disorders [3rd ed., rev.]) in a randomly selected sample (n = 1,710) of high school students at point of entry and at 1-year follow-up (n = 1,508). The Schedule for Affective Disorders and Schizophrenia for School-Age Children was used to collect diagnostic information; 9.6% met criteria for a current disorder, more than 33% had experienced a disorder over their lifetimes, and 31.7% of the latter had experienced a second disorder. High relapse rates were found for all disorders, especially for unipolar depression (18.4%) and substance use (15.0%). Female subjects had significantly higher rates at all age levels for unipolar depression, anxiety disorders, eating disorders, and adjustment disorders; male subjects had higher rates of disruptive behavior disorders.