Reversible myocardial perfusion abnormality was quantified by bull's eye and unfolded surface mapping methods in exercise thallium SPECT before and after coronary revascularization in 47 patients with angina pectoris, including 34 patients with previous myocardial infarction (PMI) and 13 with effort angina (AP). There was no difference in the incidence or extent of myocardial ischemia between the 2 groups before revascularization. However, the ischemic scores were significantly smaller in PMI group preoperatively than the reductions of the ischemic scores after revascularization. The ischemic scores, preoperatively estimated reversible perfusion abnormality was 32%, 69% and 48% of the improvement of the ischemic score (extent score, severity score, and ischemic area, respectively). Using the 3 ischemic scores, the improvement of perfusion abnormality was well predicted in 70-89% of AP patients but 35-57% of PMI patients. Thus, quantitative analysis in stress thallium SPECT is useful for detecting myocardial ischemia and evaluating the effect of coronary revascularization. However, about a half of myocardial viability was underestimated in one third of PMI patients by the conventional exercise-stress thallium SPECT study.