To examine the time course of changes in the coronary arteries in patients with coronary heart disease after aortocoronary bypass (ACB), the authors studied 2 groups of patients: (1) 23 who had conservative treatment and (2) 23 who were selected for ACB. Repeated angiography was performed 14.6 +/- 2.5 months after the initiation of the study. Following ACB, changes in lesions were observed in 17 coronary artery segments in 39.1% of the patients. Grafted artery stenoses largely proximal to the site of transplantation became progressive. There was a relationship between the changes in coronary arteries to graft patency. In Group 1, the time course of coronary atherosclerosis was found in 8 segments in 26% of the cases. Atherosclerosis progressed in all artery segments virtually in a steady way. Application of vein grafts may change intracoronary hemodynamics, creating conditions for more rapid and common progression of coronary artery lesions.