Abstract Background: Major depressive disorder (MDD) in the adolescent demonstrates a unique clinical profile, and pathogenic serotonergic dysregulation is hypothesized. Parenteral clomipramine (CMI) is known to distinguish adult MDD from control, but neurochallenge data are lacking in adolescent MDD. Methods: Thirteen drug-free outpatient adolescents who met DSM-III-R criteria for MDD were compared to adolescent controls by acute neuroendocrine and mood response to 12.5 mg of parenteral CMI. Results: Repeated measures analysis revealed significant changes from baseline for sadness ( p < .01) between groups, with normal controls increasing sadness rating after CMI. Prolactin (PRL) maximum change score from baseline was decreased in MDD relative to controls ( p < .05). Gender effects on PRL were evident in controls but not in MDD. Conclusions: The findings of PRL blunting in adolescent MDD mirrors previous work in adults. A unique finding is the induction of sadness in normal adolescent controls after CMI infusion.