To determine the long-term clinical course after percutaneous transluminal coronary angioplasty (PTCA), 841 patients, 615 with successful PTCA and 226 without, were restudied by questionnaire 2-9 years after the intervention. After successful PTCA a lasting symptomatic improvement was seen in 78% of patients vs 55% of patients without successful PTCA (p less than 0.0001). The probability of myocardial infarction 8 years after successful PTCA was 6% vs 24% after unsuccessful PTCA (p less than 0.0005). The 8-year survival probability (non-cardiac deaths excluded) was 95.7% in patients with demonstrable PTCA success, and 92.0% in patients without (p less than 0.05). Similar significant differences in favor of patients with successful PTCA were seen in the long-term prognosis of patients with single-vessel disease (n = 580). It is concluded that a long-term improvement of the cardiac prognosis by successful PTCA is probable.