1. Nomifensine is a new substance which showed, in tests for antidepressant activity, a pronounced effect which is quantitatively better than that of the reference substances. 2. With regard to thymoleptic effects in animal studies the effect of nomifensine is similar to that of tricyclic antidepressants, but nomifensine has no pronounced anticholinergic activity. 3. Nomifensine influences the cardiovascular system very slightly. 4. The mechanism of action of nomifensine differs from that of tricyclic antidepressants and must be clearly differentiated from phenylalkyl amines with sympathomimetric activity. 5. Nomifensine is a compound with a special, new profile of action, and thus cannot be calssified in known categories.