Coronary artery lesions are evaluated in a group of 43 patients surviving for more than 3 months after heart transplantation. An angiographic finding was obtained from 35 patients, autopsy findings were available in eight cases. Angiography demonstrated coronary artery lesions in 12 out of the 35 patients whereas autopsy findings were positive in five out of the eight post mortem examinations. Overall, lesions were found in 40% of patients at a mean follow-up interval of 3.5 years. While the finding of a coronary artery lesion was not related to the classic risk factors for atherosclerosis, an association to a previous cytomegalovirus or Epstein-Barr virus infection was demonstrated. The data suggest that infection caused by the two above viruses is an important factor in the development of vascular lesions in the heart transplant.