Ninety-six coronary angiographies of 30 orthotopic heart transplant recipients were studied. Eleven coronary artery fistulas to right ventricle were seen in 7 (23.3%) patients; five involved the left anterior descending artery, four the right coronary artery, and two the circumflex artery. All the coronary arterial fistulas appeared within the first year after transplantation, when endomyocardial biopsies were more frequent. In the review of the histologic samples, we found coronary arterioles greater than 0.15 mm of diameter in 3 of 7 patients with coronary arterial fistula; on the contrary, those were not found in any of the 69 histologic samples of 23 heart transplant patients without coronary fistula (p less than 0.001). Neither clinic nor hemodynamic abnormalities were seen in any patient during the follow-up. The coronary fistula had a benign course, with a tendency to decrease in size and to close spontaneously.