Percutaneous transluminal coronary angioplasty (PTCA) has become a widely accepted procedure that provides acute and medium-term relief of anginal symptoms and myocardial ischaemia. The acute success rate has risen from about 50% in the early days to approximately 90% in recent years. Serial repeat angiograms obtained in different patient groups have shown a 20% incidence of angiographically defined restenosis in patients who had been successfully treated initially. Despite the restenosis, many of these patients were symptomatically improved since the lesions shown at follow-up angiography were often less severe than those that had existed prior to original PTCA. These figures suggest that a success rate of 80% at 1 year should now be a realistic expectation, especially when patients with repeat PTCA are included. None of the 87 patients re-angiographed between 2 and 8 years after successful PTCA developed restenosis after the first year of treatment. However, new stenoses of 50% or more were found in other vessel segments, in both symptomatic and asymptomatic patients, at a rate of about 7% per year.