The consequences of restenosis after angioplasty were evaluated in 466 patients who had coronary angiography 3 to 12 months after successful coronary angioplasty and were followed long term. The 236 subjects with restenosis resembled the 230 without restenosis with respect to age, sex, presence of multivessel disease, mean ejection fraction, prior myocardial infarction, prior coronary artery bypass grafting, and completeness of revascularization. The 5-year relative risk of revascularization for patients with restenosis markedly exceeded that for patients without restenosis. The relative risk of repeat angioplasty in the former group was 4.26 times that in the latter group (95% confidence interval, 2.80 to 6.51), and the risk of coronary artery bypass grafting in patients with restenosis was 3.68 (95% confidence interval, 2.16 to 6.28). There was no difference between the 2 groups in the relative risk of myocardial infarction or death. When the completeness of revascularization was considered, patients with incomplete revascularization and restenosis had the worst outcomes, with 50% needing coronary artery bypass grafting within 5 years. Early restenosis markedly increases the probability of revascularization, but it has little effect on infarction or mortality. Even when early restenosis is absent, further revascularization procedures are still frequent. A solution to the problem of restenosis might reduce by half the need for revascularization during the subsequent 5 years.