Percutaneous transluminal coronary angioplasty is a promising new method of treatment for patients with coronary artery disease. Inflation of a balloon located at the tip of a catheter is used to dilate stenoses. In the 1st yr of the use of percutaneous transluminal coronary angioplasty at the Mayo Clinic, it was applied in 34 selected patients whose severe angina pectoris was related to a single, high-grade coronary artery stenosis. Successful dilation (stenosis opened by 40% or more of the normal luminal diameter) was achieved in 22 patients (65% of the total). Early postangioplasty assessment indicated relief of angina in all of these patients except for one patient who demonstrated coronary spasm that was responsive to medication. Median hospital stay was 3 days. Failure of percutaneous transluminal coronary angioplasty in the remaining 12 patients was usually due to an inability to manipulate the balloon catheter across the stenotic segment. Eleven of these patients had saphenous vein bypass graft surgery, as planned, immediately after the attempted angioplasty. There were no deaths, but 3 patients sustained a transmural myocardial infarction. This initial experience with percutaneous transluminal coronary angioplasty indicates that it is a relatively safe and a frequently effective method of relieving coronary stenosis in selected patients with symptomatic coronary artery disease.