Retrospective analysis of 4886 adults undergoing coronary arteriography for evaluation of angina between October 1988 and December 1991, revealed coronary artery fistulae in eight patients (all men, aged 36-69 years). No murmur was audible in any of these eight patients. Associated significant coronary artery disease was detected in five patients. The feeder arteries to the fistula were both the left main coronary artery and the left anterior descending artery (LAD) in two, the LAD in six, and the right coronary artery in two patients. The fistula terminated in the pulmonary artery in seven patients and in the right atrium in one patient. Successful operative treatment (coronary artery bypass grafting and ligation of the fistula) was undertaken in four patients with severe obstructive coronary artery disease with satisfactory results. Follow-up for up to 2 years of the three patients with coronary artery fistula and no associated coronary artery disease who did not undergo surgery revealed continuing good prognosis. We conclude that coronary artery fistula in adults is a distinct, though rare (incidence in present series 0.11%) entity, without audible murmur, commonly associated with coronary artery obstructive disease, and that the diagnosis is mostly incidental during routine coronary arteriography.