Lofepramin is a new derivative of imipramine. Its effects and side effects were compared to those of imipramine in a double-blind trial. 49 hospitalized patients, suffering from endogenous depression, were treated for 20 days with 210 mg lofepramin daily and 52 other patients with 150 mg imipramine daily. The results of the repeated psychiatric examinations were documented using the AMP system. Both substances proved to have high antidepressant effects and showed no significant difference in the quality of their effects.