We undertook a double-blind, placebo-controlled study to determine the effectiveness of verapamil hydrochloride for the prophylaxis of migraine. Twelve patients were given either verapamil hydrochloride, 80 mg four times daily, or placebo in random order during two consecutive three-month periods. Migraine frequency, severity, and duration were quantified by daily logs and monthly questionnaires. Ten of the 12 patients had fewer migraines during verapamil therapy. Migraine frequency decreased from 6.7 to 3.8 migraines per patient per month, for a mean decrease of 49%. Headache unit index fell from an average of 0.61 to 0.44. We conclude that verapamil is effective in the prophylaxis of migraine and that verapamil might be considered one alternative in the development of a regimen for the prophylaxis of migraine.