Δ9-tetrahydrocannabinol (THC), given under double-blind conditions to eight hospitalized depressed patients for periods of up to seven days, failed to produce significant euphoria or an antidepressant response during the period of administration. Four patients who received the drug for seven days showed little change in mood but reported considerable drowsiness. In four patients, the drug trial was shortened because of adverse reactions; two of these patients experienced severe anxiety reactions with depersonalization after a single dose. Effects on cognitive functioning and vital signs were similar to those reported by other investigators in normal subjects. We should like to emphasize that our results were obtained with a small sample of hospitalized inpatients with moderate to severe depression. Different effects might be observed in other settings or in patients with less severe depressive symptoms.