Drugs which block adrenergic receptors have previously been used in the prophylactic treatment ofmigraine with varying success. We report a double blind crossover trial with the ß-blocker acebutolol(Sectral, May & Baker Ltd) in which 43 patients took part. The number, frequency, duration and intensity of the headaches were recorded by the patients and results were analysed for the 33 patients who completed the trial. Plasma levels of acebutolol were measured during the trial. There was good patient compliance but here was no obvious correlation found between any of the parameters measured and the concentration of the drug. Although there was a general reduction in frequency with intensity of migraine during treatment when compared with a pre-trial period, there was also a large placebo effect which made it difficult to separate the true effect of the ß-blocking drug. 13 patients, however, said that they felt better during the period of the trial when they were receiving acebutolol and continued on this treatment when the trial finished. The value of acebutolol therefore requires further evaluation in such patients.