There have been several case reports of improvement in tardive dyskinesia (TD) after treatment with calcium-blocking agents. We have conducted prior single-blind (rater-blind) studies of verapamil and diltiazem and found a statistically significant improvement in TD with verapamil, and a small improvement that did not reach statistical improvement after diltiazem treatment. We now report a single-blind (rater-blind) study of a third calcium antagonist, nifedipine, in the treatment of TD. Nifedipine (30-60 mg/day) was administered to eight schizophrenic patients with TD. Mean AIMS scores on items 1-7 decreased from 12.9 +/- 2.0 (SD) at baseline to 10.8 +/- 2.7 after treatment (t = 3.66, p = 0.01). All subjects were able to tolerate the maximal dose of nifedipine without significant side effects. TD is known to be affected by drugs that affect dopamine neurotransmission. Several lines of pre-clinical and clinical evidence suggest interactions between the calcium antagonists and the CNS dopamine system and provide a possible explanation for the effects on TD seen with calcium antagonists.