Between January 1979 and October 1991, percutaneous transluminal angioplasty of stenosed or occluded coronary bypass grafts was attempted 180 times in 146 patients (180 lesions in 157 bypass grafts); 6/157 grafts were internal mammary grafts. The procedure was successful in 129/157 grafts (82%) and in 151/180 lesions (84%). Failures occurred almost exclusively in recanalization attempts. Cardiac complications occurred in 4/146 patients (2.7%). Three patients developed an acute myocardial infarction, another patient died after acute occlusion of a native vessel dilated during the same procedure. In successful attempts the severity of stenosis was reduced from 87 +/- 10% to 33 +/- 15%. 113/129 successfully dilated grafts had at least one (mean 2.7) control angiogram. 54/113 (48%) showed recurrence after a mean follow up of 6 months. An additional 15 grafts showed late restenosis in a second control angiogram (mean follow-up 23 months). The total restenosis rate was 61%. Restenoses were dilated again one to six times (mean 1.9) with comparable success and recurrence rate. Two patients died during the sixth angioplasty. Finally, 32/129 (25%) grafts were occluded or presumably occluded, and 97/129 (75%) were angiographically confirmed open without restenosis. Thus, angioplasty of bypass grafts is an alternative to a repeat revascularization surgery. The acute results are comparable to the results of angioplasty in native coronary arteries. The restenosis rate is high. One has to be aware of late restenosis. Restenosis can be dilated repeatedly with a comparable success rate and with no significant increase in restenosis rate.