The long-term results of percutaneous transluminal coronary angioplasty were evaluated in our first 42 patients, who had initial successful angioplasty and no restenosis on angiogram performed four months after angioplasty. Evaluation included repeat follow-up angiogram performed approximately two years after angioplasty in 22 of the 42 patients. All 42 patients had single vessel disease with severe angina pectoris refractory to medical treatment before angioplasty; at a mean follow-up of 28 months after angioplasty, 37 (88%) were asymptomatic. No patient died or underwent coronary artery bypass graft surgery during the follow-up period, although three patients (7%) suffered a myocardial infarction due to occlusion of a nondilated artery. In the 22 cases studied at a mean of 28 months after angioplasty, angiogram showed that successful coronary artery dilatation remained in all cases, with no deterioration of a dilated lesion between the four and 28 month angiograms. Progression of atherosclerosis, however, did occur in five of the 22 patients (23%), with development of either stenosis or occlusion of a non-dilated vessel. This study suggests that the development of restonsis between four and 28 months after percutaneous transluminal coronary angioplasty is unlikely. The results suggest an excellent long-term prognosis after angioplasty, in patients who have no evidence of restenosis at four months after an initially successful dilatation.