T1-201 stress myocardial scintigraphy was performed in 35 cases of ischemic heart disease (angina pectoris and myocardial infarction) to assess the accuracy of SPECT and bull's eye display in the quantitative diagnosis of coronary artery lesions. We evaluated the sites of ischemic heart disease using the following methods: 1. SPECT (visual): visual evaluation by myocardial SPECT images. 2. SPECT +bull's eye (visual): visual evaluation by stress, delayed and washout images of bull's eye display. 3. bull's eye (quantitative): quantitative evaluation by the washout rate and % uptake. The diagnostic accuracy of method 2 was higher than that of method 1 in all coronary arterial vessels; LAD (74% vs 80%), LCX (60% vs 63%) and RCA (57% vs 60%). The diagnostic accuracy of method 3 was approximately equal to that of method 2. The diagnostic accuracy of method 2 was higher than of method 1 in patients with three-vessel disease (43% vs 67%), while there was no such difference in patients with both single and two-vessel disease. Moreover, the diagnostic accuracy of method 3 was approximately equal to that of method 2 in patients with three-vessel disease. In some cases the redistribution was recognized only by using washout images or by calculating the washout rate as a quantitative evaluation. In conclusion, the bull's eye display improved the diagnostic accuracy of T1-201 scintigraphy, but the quantitative analysis did not further improve the accuracy. However, there were some possibilities of evaluating the redistribution in some cases by using quantitative analysis.(ABSTRACT TRUNCATED AT 250 WORDS)