In the present double-blind controlled study the efficacy and safety of fluoxetine 20 mg/day versus clomipramine 75 mg/day was evaluated during 5 weeks of treatment in 30 hospitalized patients. The sample was selected according to DSM III criteria for major depressive disorders with a score of at least 18 on the first 17 items of the Hamilton Rating Scale for Depression (HRSD). Therapeutic efficacy was evaluated weekly by using HRSD, Zung Self Rating Scale for Depression, Montgomery-Asberg Scale for Depression, Clinical Global Impression for severity and improvement of depressive symptoms. Safety was monitored weekly by recording body weight, blood pressure, pulse rate, temperature, physical conditions, laboratory tests, adverse experiences and concomitant medication. The results confirm the effectiveness and good tolerability of fluoxetine in the treatment of depressive disorders.