Nimodipine (BAY e 9736), a new dihydropyridine derivative, has been shown to reduce neurological deficits and mortality induced by acute cerebral ischemia in experimental studies. We investigated the effects of this calcium antagonist in patients with acute ischemic stroke through a randomized, double-blind, parallel-designed trial in which nimodipine was compared with placebo. Forty-one of 54 screened cases were found to fulfil the inclusion criteria (sudden occurrence of a focal neurological deficit secondary to an acute ischemic event in the carotid area diagnosed after a complete neurological work-up) and entered the study. Nineteen of them were treated with nimodipine (40 mg t.i.d. administered for 28 days) and the remaining 22 with placebo, given in identical tablets. In all patients the treatment started within 12 h after the onset of the symptoms. Course and intensity of the neurological deficit were evaluated by the Mathew Scale (slightly modified). Forty patients concluded the trial. Nimodipine was withdrawn in one case following the occurrence of a skin rash whose causative relation with the test drug could not be clarified. Altogether, however, nimodipine was well tolerated and no severe cardiovascular adverse reactions were observed. In terms of efficacy, the scores obtained by the Mathew Scale showed a higher rate of improvement on nimodipine than on placebo, thus indicating that patients receiving the latter drug did not fare as well as those receiving the test medication. Our data suggest that nimodipine may be beneficial in the treatment of acute stroke.