OBJECTIVE: The primary objective of this investigation was to examine the acute antidepressant effects of intravenous hydrocortisone and ovine corticotropin releasing hormone (CRH) infusions in patients with major depression. METHOD: Twenty-two patients who met DSM-III-R criteria for nonpsychotic major depression were randomly assigned to receive intravenously 1 mg/kg of ovine CRH, 15 mg of hydrocortisone, or saline under double-blind conditions on day 1. Standard depression rating scales were completed on day 1 before the study medications were administered and again the following day (day 2). RESULTS: Patients treated with hydrocortisone demonstrated a significantly greater reduction in total 21-item Hamilton Depression Rating Scale scores (mean reduction=8.4 points or 37%) than patients given ovine CRH (mean=1.2 points) or placebo (mean=1.3 points). CONCLUSIONS: Acute hydrocortisone infusion is associated with a rapid and robust reduction in depressive symptoms. The authors discuss the therapeutic implications of these findings.