Exercise 201Tl single photon emission computed tomography (Ex-SPECT) was performed before and after percutaneous transluminal coronary angioplasty (PTCA) to detect ischemia and determine the response of the ischemic myocardium. In a series of 132 patients with angina pectoris, 43 were followed up by Ex-SPECT and coronary angiography. Before PTCA, ischemia was detected in 85% of the patients, and in all cases a diameter stenosis (%DS) of 90% or more was seen. After PTCA, 90% of the patients showed improvement of ischemia. An excellent correlation between the pressure gradient (PG) as determined during PTCA and the washout rate (WR) suggests that the WR can be used as a measure for myocardial perfusion in the areas related to coronary stenosis. During follow-up by Ex-SPECT, 34 patients were found with redistribution, and restenosis was present in 59% of these patients. In comparison with the images obtained one week after PTCA, a further improvement was confirmed by Ex-SPECT during follow-up in 5 of 20 patients without restenosis. Ex-SPECT proved to be of use in evaluating the response of the ischemic myocardium to PTCA, as well as the therapeutical effects and the degree of restenosis. Long-term follow-up revealed that some patients had areas of hibernating myocardium.