To evaluate the area at risk and the myocardial viability of acute myocardial infarction (AMI), we compared rest 123I-beta-methyl iodophenyl pentadecanoic acid (123I-BMIPP) and 201Tl myocardial SPECT with 201Tl/99mTc-PYP dual SPECT (D-SPECT) in 65 patients (mean age 64 +/- 11 years) with AMI. D-SPECT was performed in 3 to 5 days, 123I-BMIPP myocardial SPECT in 5 to 7 days, and left ventriculography on 1 month after onset of AMI. Furthermore, 201Tl/123I-BMIPP myocardial SPECT and left ventriculography were performed on 4 months after onset of AMI. The area which showed the reduced 123I-BMIPP uptake was larger than that showed the accumulation of 99mTc-PYP. The improvement of regional wall motion on 4 months after onset of AMI tended to be more closely correlated with the existence of discrepancy zone between 201Tl and 123I-BMIPP uptake than that of overlap zone between 201Tl and 99mTc-PYP uptake in acute period. We conclude that 201Tl/123I-BMIPP myocardial SPECT is more useful to evaluate the area at risk and myocardial viability of AMI than D-SPECT.