Assessment of percutaneous transluminal coronary angioplasty (PTCA) by early radionuclide exercise test was evaluated for 11 arteries undergoing a successful procedure. Exercise thallium-201 (Tl-201) and radionuclide ventriculography (RNV) were performed within 3 days before and after PTCA and compared to % diameter stenosis, % translesional gradient and regional coronary flow reserve (CFR) determined by digital coronary angiography. Primary success of the procedure was gauged by reduction in % stenosis from 80 +/- 12% to 31 +/- 12% (residual stenosis less than 50% in all cases) and reduction in % gradient less than 25% in all cases). Before PTCA, Tl-201 and/or RNV were abnormal in all cases. After PTCA, radionuclide exercise tests improved but remained abnormal in 4 instances. No relationship was found between residual % gradient or stenosis and pathological Tl-201 or RNV following PTCA, but abnormal tests were observed among 4 out of the 5 vessels with the lowest CFR (less than 1.69). In one case CFR remained depressed despite good angiographic, hemodynamic and scintigraphic results, this patient had unstable angina before the procedure. Among patients with stable symptoms, CFR of arterial distributions with positive Tl-201 or RNV after PTCA was significantly lower than that with negative tests (1.58 +/- 0.05 as compared to 1.90 +/- 0.25, P less than 0.02). Early radionuclide stress tests results thus reflect the physiologic improvement of coronary circulation. They may reflect the persistence of coronary flow abnormalities despite the relief of the epicardial stenosis.