To permit comparison of percutaneous transluminal coronary angioplasty (PTCA) with conventional therapy, the clinical outcome was established in patients who would have been suitable candidates for PTCA but who presented before the technique was available. Coronary angiograms were reviewed of patients who met the following criteria: single-vessel disease with proximal subtotal coronary stenosis, chest pain of at least class II, and cardiac catheterization before 1981. Angiograms were evaluated according to established criteria for PTCA by an experienced angiographer. One hundred ten patients (2.1% of the patient population) were judged suitable for PTCA. Clinical and catheterization findings closely resembled those of patients in the national PTCA registry. Five years after catheterization, 97% of PTCA candidates treated medically were alive and 85% had not had myocardial infarction. Forty-six patients had coronary artery bypass surgery within 6 months of catheterization and 10 other patients had subsequent surgery. Five years after surgery, 91% were alive and 87% had not had myocardial infarction. At 6 months of follow-up, 78% of all patients had improved at least 1 functional class, and 86% of all patients working before catheterization were still employed. Functional capacity was well maintained during long-term follow-up (median 6.5 years, range 1.4 to 12.2). These data indicate that PTCA candidates have an excellent prognosis for survival, a low risk of infarction, and well-maintained functional capacity when revascularization is reserved for those with inadequate control of symptoms by medical therapy.