The incidence of acute and late complications after coronary stenting has been studied in 95 consecutive patients. A total of 113 stents were implanted: 23 cases for acute occlusion of the dilated vessel and 72 for restenosis. After 16 months of follow-up, minor complications had occurred in 22 patients (23%). They consisted of transient occlusion of the prosthesis in 7 patients (7.3%), non-Q wave infarction in 4 patients (4.2%) and 10 hemorrhages (11%). During the following period major complications were observed in 11 patients (12%) with myocardial infarction in 7 instances and acute occlusion in 7 patients. 5 patients (5.3%) underwent coronary artery bypass graft and 6 (6.3%) died (one in-hospital death). Two deaths were related to the stent, but in the other four no definite correlation between the prosthesis and the death could be demonstrated. Restenosis at 12 months was present in 4 cases: in 3 patients (4.7%) where the stent had been implanted for restenosis and 1 (4.7%) where it had been implanted for acute occlusion. We conclude that for selected patients, coronary stenting is a promising new technique, especially for acute occlusion after PTCA; moreover, at 12 months restenosis is less frequent than after PTCA. However, technical improvement is necessary to diminish the rate of complications, particularly thrombosis and hemorrhage.