The prophylactic effect of nimodipine in the treatment of migraine headache was assessed in a prospective, placebo-controlled, double-blind trial. Twenty-six patients were studied during a 3-month experimental period (placebo vs nimodipine) following a 1-month period during which all patients received placebo. Results were tabulated using a “headache index”. A trend in favour of a beneficial nimodipine effect on the headache index was demonstrated which achieved statistical significance during one month of the follow-up period. A similar trend with respect to the overall number of headaches was demonstrated and achieved statistical significance during two months of the follow-up period. We conclude that nimodipine is a potentially useful agent in the prophylaxis of migraine headache.