We report the immediate results and 6 month follow-up data of 494 consecutive patients who underwent coronary angioplasty in two or more major epicardial arteries. Clinical success was achieved in 95% of the 494 patients. The technical success rate of the 1,117 vessels dilated was 89%, defined as at least a 35% reduction (mean = 53%) of the initial percent diameter stenosis and a decrease in the transstenotic gradient to less than or equal to 15 mmHg (mean = 9 mmHg). Complications of the procedure included emergency bypass surgery (2.8%), myocardial infarction (3.0%), and hospital death (0.4%) inclusive. At least one of these complications (major cardiac event) occurred in 3.8% of patients. Prior to angioplasty, 46% of patients were in Canadian Cardiovascular Society Class II, 42% in Class III, and 12% in Class IV. Follow-up clinical evaluation (mean follow-up period of 16.9 months) showed 83% of patients in Class I, 14% in Class II, and 3% in Class III. Of the 286 successful patients who have reached 6 month follow-up plateau (mean follow-up period of 20.5 months), 164 (57%) have so far had repeat coronary angiography and exhibited three different patterns: all lesions patent (N = 54), some lesions restenosed (N = 60), and all lesions restenosed (N = 32). There were 18 patients with new vessel lesions (not previously dilated). Logistic regression analyses demonstrated that clinical factors including diabetes (P less than .05), hypercholesterolemia, (P less than .01), new onset angina (P less than .05), current smoking (P less than .01), and morphologic and technical factors such as preangioplasty diameter stenosis greater than 95% (P less than .05) and higher balloon inflation pressure (P less than .05) were predictive of increased risk of recurrence. Patients were classified into two groups based on the anatomy of the target lesions. In Group A (N = 217), patients had a single lesion in each of the vessels to be dilated; Group B (N = 277) patients had a complex lesion in at least one of the vessels dilated. Group B patients were more likely to develop recurrence (P less than .05). Of the original 494 patients, 488 (99%) are alive. Coronary angioplasty (either initially or with repeat PTCA) has been the definitive treatment in 453 of the 494 patients for an overall success of 92%.(ABSTRACT TRUNCATED AT 400 WORDS)