Percutaneous transluminal coronary angioplasty (PTCA) was performed in 14 patients with significant left main stem stenosis following protective coronary artery bypass grafting (CABG). The procedure was successful in 13/14 patients (93%), achieving a decrease in mean diameter stenosis from 74% +/- 7% to 31% +/- 12% (P less than 0.01). Accordingly, the absolute stenosis diameter increased from 0.9 mm +/- 0.3 mm to 2.4 mm +/- 0.5 mm (P less than 0.01). Dissection of the left main stem artery and a transient significant fall of blood pressure each occurred in one patient. No other serious complications were noted. Eight of 13 patients (62%) with successful PTCA underwent control angiography. Restenosis had occurred in 3 of 8 patients (38%) with total occlusion of the left main stem in 1 patient. All bypass grafts were found to be patent at follow-up. Clinical evaluation in all 14 patients revealed no serious events (death, myocardial infarction, repeat revascularization procedure) during a mean follow-up period of 27 months (range 6-39 months). PTCA of the left main stem following CABG can be considered a relatively safe and effective procedure with a marked restenosis-rate but beyond that, an uncomplicated long-term follow-up.