PURPOSE: To evaluate the results of coronary angioplasty in patients at the age of 40 years old or under. METHODS: From July 1987 to July 1990, 878 coronary angioplasty procedures were performed. Sixty six patients (7.5%) were 40 years old or under. The coronary obstruction was considered significant when 70% or more of the arterial diameter was involved and the post angioplasty results were considered satisfactory when residual obstruction was less than the 50%. RESULTS: Fifty four patients (81.8%) were male with an average age of 37 years (ranging from 29 to 40). Forty four patients (67%) had stable angina, 18 (27%) unstable angina, 3 (4%) acute myocardial infarction (AMI) and one (1.5%) AMI after streptokinase treatment. Eight of these patients had previous report of AMI and 3 (4.5%) had undergone coronary bypass grafting surgery. Fifty five patients (83%) had single vessel disease and 11 (17%) had multivessel disease. Eighty coronary arteries had balloon dilatation. In 32 patients (58%) with single vessel artery, 12 (22%) in the RCA, 10 (18%) in the left circumflex and one (2%) into a saphenous vein bypass grafting. In 12 patients (48%) with multivessel disease it was performed in the LAD coronary artery, 8 (32%) in the RCA and 5 (20%) in the left circumflex. Angioplasty was successfully performed in 53 (96%) patients with single vessel disease and in 10 (01%) with multivessel disease. One of the patients died immediately after the procedure. A follow up of 11.6 months (ranged from 1 to 27 months) was possible in 63 patients. Re-stenosis was depicted in 10 (19%) of the 55 patients with single vessel disease and in 3 of the 11 patients (30%) with multivessel disease. Nine patients had a successful redilatation in the first group and 2 in the second one. The two remaining patients had undergone coronary bypass surgery. The clinical evaluation among patients who had been dilated as the first procedure and those who had redilatation (61 patients) showed: 92% were asymptomatic and 8% had mild angina. CONCLUSION: Coronary angioplasty performed in young patients is an effective procedure with very low rate of early complications and favorable clinical follow-up.