The 3 to 5-year clinical outcomes of 627 consecutive patients selected for treatment with percutaneous transluminal coronary angioplasty (PTCA) at Emory University Hospital for one- or two-vessel coronary artery disease with involvement of the left anterior descending coronary artery, between July 1981 and June 1983, and 865 patients in the Coronary Artery Surgery Study with similar coronary artery disease involvement selected for medical therapy between 1975 and 1979 were compared. Cox analyses and stratified life table analyses were used to adjust for differences in 13 variables including concurrent medical therapy. Complete follow-up was obtained in 97% of PTCA patients and 99% of medically treated patients. After correction for baseline differences in significantly predictive variables, there was no difference between the relative risk of death after PTCA vs medical therapy (RR = 0.7; p = 0.36). However, results of analysis of prospectively defined subsets showed a potential survival benefit after PTCA for patients with an ejection fraction less than 50% (RR = 0.2; p = 0.02) and also for patients with two-vessel disease (RR = 0.2; p = 0.04). For the groups as a whole there was no difference in risk of infarction after PTCA and medical therapy (RR = 0.8; p = 0.58). However, for patients with 90% to 99% LAD stenosis there was a trend toward lessened risk of infarction after PTCA (RR = 0.6; p = 0.15). No patient subset had a higher risk of death or infarction with PTCA (p less than or equal to 0.15). The likelihood of later surgery was increased after PTCA (RR = 1.5; p = 0.002). Angina, employment, and activity levels were improved after PTCA. Thus PTCA compared to medical therapy was associated with improved functional status and may decrease the risk of death and infarction in certain patient subsets. However, bypass surgery was more often performed in patients initially treated with PTCA. These data should be interpreted in light of their nonrandomized study origin and generation from different clinical sites.