Resumen:Part I of this review critically evaluates antidepressants' benefits for children and adolescents with affective disorders. The effectiveness of antidepressants is characterized with specific references regarding diagnostic methodology, measurement characteristics, response definitions, recovery rates, length of treatment, and plasma level monitoring. Antidepressants' efficacy for depressed youths is quite circumscribed, and their superiority to placebo remains unproved. Their intriguing lack of efficacy in affective disorders is discussed based on methodological issues and from a theoretical perspective. Clinical and research implications are presented.