In percutaneous transluminal coronary angioplasty, a catheter system is introduced through a systemic artery under local anesthesia to dilate a stenotic artery by controlled inflation of a distensible balloon. Over the past 18 months, we have used this technic in 50 patients. The technic was successful in 32 patients, reducing the stenosis from a mean of 84 to 34 per cent (P<0.001) and the coronary-pressure gradient from a mean of 58 to 19 mm Hg (P<0.001). Twenty-nine patients showed improvement in cardiac function during follow-up examination. Because of acute deterioration in clinical status, emergency bypass was later necessary in five patients; three showed electrocardiograpic evidence of infarcts. Patients with single-vessel disease appear to be most suitable for the procedure, and a short history of pain indicates the presence of a soft (distensible) atheroma likely to respond to dilatation. We estimate that only about 10 to 15 per cent of candidates for bypass surgery have lesions suitable for this procedure. A prospective randomized trial will be necessary to evaluate its usefulness in comparison with surgical and medical management. (N Engl J Med 301:61–68, 1979) IN 1964, Dotter and Judkins1 introduced the technic of transluminal angioplasty for the treatment of atherosclerotic obstruction of the femoral artery. Despite their enthusiasm, the technic has been largely ignored in the United States. In Europe, however, several physicians have used this technic to treat large numbers of patients.2 Because of the technical difficulties, complications and limited usefulness of transluminal angioplasty in the treatment of obstruction of the peripheral arteries, we sought to modify the original technic of Dotter and Judkins. A double-lumen dilatation catheter with a nonelastic balloon was developed.3 Such catheters have been used since February, 1974, in. © 1979, Massachusetts Medical Society. All rights reserved.