Aim To investigate the value of rest 99m Tc-MIBI myocardial single photon emission computed tomography(SPECT) in diagnosis of old myocardial infarction.Methods Vector cardiogram(VCG),ultrasonic cardiography(UCG) and rest 99m Tc-MIBI SPECT were performed in the 25 patients with dubious old myocardial infarction(22 inferior and 3 anterior myocardial infarction).Positive rate of rest 99m Tc-MIBI SPECT myocardial imaging were compared with VCG and UCG for diagnosis of old myocardial infarction.Results In diagnosis of old myocardial infarction,positive rate of rest 99m Tc-MIBI SPECT was 88%,and were significantly higher than VCG(32%) and UCG(24%;P<0.05).In diagnosis of old inferior myocardial infarction,positive rate of rest 99m Tc-MIBI SPECT(82%) were significantly higher than VCG(27%) and UCG(23%;P<0.05).Consistent rate of rest 99m Tc-MIBI SPECT with angiography was higher than the VCG(100% vs 25%).Conclusion In diagnosis of old myocardial infarction especially inferior myocardial infarction,rest 99m Tc-MIBI SPECT myocardial imaging has significant clinic value.