To clarify the clinical significance of regional myocardial perfusion abnormality of the left ventricle in dilated cardiomyopathy (DCM), 20 patients with DCM underwent dipyridamole Tl-201 emission computed tomography (ECT). The subjects were divided into 2 groups: group 1 had (n = 9) reversible defects and group 2 (n = 11) had persistent defects only. Group 2 patients significantly advanced heart failure and significantly poorer prognoses than group 1 (55% vs 11% in 2 years survival rate, p less than 0.05). The echocardiographic left ventricular end-diastolic dimension was larger in group 2 than group 1 (68.3 +/- 8.2 mm vs 61.9 +/- 4.0 mm, p less than 0.05) and % fractional shortening was smaller in group 2 than group 1 (18.0 +/- 4.5% vs 24.5 +/- 6.9%, p less than 0.05). Moreover, 12 of the 13 segments with reversible defect showed fairly well preserved left ventricular wall motion, whereas 35 of 58 segments with persistent defect had severely impaired wall motion (1/13 vs 35/58, p less than 0.01). Dipyridamole Tl-201 ECT demonstrated conclusively that the two types of defects (reversible and persistent) are useful to evaluate not only the abnormal myocardial perfusion but also myocardial damage and the prognosis in DCM.