The evidence of continuity of child and adolescent depression into adult depression, of familial transmission of this disorder from parent to child, of psychobiologic similarity, and the similar syndromic picture all strongly argue that, by extrapolation, pharmacologic agents with proven efficacy in adult depression are likely candidates for the pharmacologic treatment of children and adolescents with this disorder. On the other hand, differences in kinetics, in cognitive maturity, and in brain maturity effecting mechanisms thought to be important in the control of affect all strongly argue that even if the disorder is related, the pharmacologic response may be different. As yet, the efficacy or lack of efficacy of cyclic antidepressants in either children or adolescents with MDD have not been established.