To address the question of whether infarct size after thrombolysis can comparably be estimated by thallium SPECT scintigraphy and contrast cineangiography, 32 patients in whom regional wall motion abnormality had been assessed by means of the "centerline" method, 10 to 21 days after infarction, underwent biphasic thallium SPECT scintigraphy with dipyridamole. There were no statistically significant correlations between left ventricular ejection fraction and the degree of hypokinesia in the infarct area on one hand, and thallium defect size in the early and late scintigram on the other. Hypokinesia was inversely correlated (r = -0.51) with the time interval from symptom onset to reperfusion, but no such correlation was found between thallium defect size and this parameter. In patients in whom reperfusion was achieved within 3 h of symptom onset, hypokinesia was significantly less (-1.11 +/- 0.6 standard deviations (SD] than in patients in whom reperfusion was achieved later (-2.16 +/- 0.8 SD; p less than 0.01). Thallium defect size, however, was not different in these two groups of patients. It is concluded that there is no close correlation between regional wall motion abnormality assessed subacutely after thrombolysis and infarct size determined by SPECT in the chronic state. Thus, impairment of left ventricular function may not be assessed from scintigraphic findings.