The reliability of assessment of Research Diagnostic Criteria and DSM-III axis I affective disorders in children and adolescents was studied using a semistructured diagnostic interview. The Schedule for Affective Disorders and Schizophrenia (SADS) for School-Age Children (Kiddie SADS) Present Episode Version, an adaptation of the adult SADS for children was used. Fifty-two subjects, aged 6 through 17 years, were interviewed in a test-retest format by one of three pairs of interviewers. Assessment of symptoms and composite scales of the depressive syndrome were determined to have acceptable reliability, as were three depressive diagnoses. Conduct disorder was assessed with high reliability. Four anxiety disorders and their composite symptoms were assessed with unacceptable reliability; only separation anxiety was assessed with acceptable reliability. The results of this study showed generally lower reliability of symptoms, scales, and diagnoses than did two studies of adults using the SADS.