Eighty-three migraine patients were admitted to a double-blind, single cross-over, propranolol vs. placebostudy. Sixty-two patients completed the trial. The daily dosage was either 80 or 160 mg. propranolol, or an equivalent number of placebo capsules, for 4 to 8 weeks for the first medication and 8 weeks for the second one. At the end of the trial, 32 patients preferred propranolol and 18 placebo. Those who preferred propranolol had greater reduction in severity and frequency of headaches and less consumption of analgesics and ergotamine than patients who preferred placebo. Side effects were benign. Propranolol issafe and effective for the prophylaxis of migraine if patients are carefully selected.