The effects of moclobemide (300–600 mg/day), a reversible monoamine oxidase inhibitor – A (MAOI-A), were compared in a double-blind, multi-centre trial with those of clomipramine (100–200 mg/day) on 129 in-patients suffering from endogenous depression (according to ICD–9 and the Newcastle Scale). No significant differences in efficacy were seen between the two treatment groups. In the moclobemide group the mean scores on the MADRS were 36.4 on day 0 and 13.2 on day 42 (end-point analysis); scores were 37.4 and 10.9 respectively in the clomipramine group. An earlier onset of antidepressant activity was noted for moclobemide. Tolerability was significantly better for moclobemide, as shown by the Clinical Global Impression of Tolerance (CGIT). Anticholinergic effects, weight gain and orthostatic hypotension were more frequent in the clomipramine group. No biological treatment-related changes were observed.