Perhexiline maleate, which has no beta adreno-receptor-blocking activity, has been suggested as an effective prophylactic agent for angina pectoris. The effects of perhexilline were compared with those of placebo by a double-blind crossover trial in seven patients with moderate to severe angina pectoris. Attack rates and glyceryl trinitrate consumption were significantly lower during the perhexilline phase than during the placebo phase of treatment. There was also a mild fall in resting heart rate. Three patients who had failed to respond to beta adrenoreceptor-blocking drugs, and one who had suffered reccurrence of symptoms after coronary artery surgery responded favourably to perhexiline. It thus appears that perhexiline maleate is an effective and potentially valuable agent in this condition.