Coronaro-pulmonary fistula (CPF) is a rare congenital malformation comprising about 17 p. 100 of coronaro-cardiac fistulae. The authors report a series of 10 cases of CPF diagnosed in over 6 000 coronary angiographic studies. This material includes 7 cases of "proximal" CPF in which the receiving vessel was the main pulmonary artery (MPA), there were two cases of fistula between the coronary and distal pulmonary arteries ("distal" fistulae), one of which had an associated proximal CPF; finally one case showed abnormal vascularisation of part of the lung by a branch of the left circumflex artery. The left coronary artery was involved in all 8 cases of proximal CPF, confirming previously published data. The communication comprised a single pedicle or a plexus arising from the initial segment of the coronary artery and draining into the MPA in all cases. Coronary angiography was performed in the 5 men and 3 women (average age 53 years) for chest pain (2 cases) acute ischaemia in the territory of the left anterior descending artery (1 case), residual post-infarction angina and assessment after infarction (2 cases), mitral valve disease (2 cases) and for a continuous murmur (1 case). The ECG was normal in 2 cases; 5 patients had ST abnormalities; left ventricular hypertrophy was observed in 2 cases but these patients had associated mitral valve disease. Radiological cardiomegaly was present in 2 cases. Finally, no significant left-to-right shunt could be detected on cardiac catheterisation. The outcome was favourable in 7 patients (resection of fistula and eventual coronary bypass surgery in 3 cases; surgical abstention in the remainder).(ABSTRACT TRUNCATED AT 250 WORDS)