The antidepressant effect of rolipram, believed to be based on a new mechanism of action, was investigated in an open phase II study in 10 depressive patients, most of whom had been refractory to previous antidepressant therapy. Five patients displayed a good to very good improvement of their depressive condition. Four patients failed to show any substantial improvement, and therapy had to be withdrawn in one case due to deterioration of the condition. In most cases, the antidepressant effect of the trial preparation became noticeable after 2-4 days of treatment only. Basing on the presented cases, the tolerance can be described as excellent compared to other antidepressants. Although, on the whole the trial yielded very encouraging results, only double-blind trials can determine the true antidepressant efficacy of rolipram.