To find latent heart disease in diabetic patients, 142 diabetic patients were divided into 4 groups: 1) No hypertension and normal ECG (DM group); 2) Hypertension recognized clinically (HT group); 3) Myocardial damage on ECG (MD group) 4) group associated with the previous 2 (HT + MD group). In all groups Tl-201 exercise myocardial scintigrams and blood pool scintigrams were taken for comparative analysis. Positive rates of SPECT were 27.7% (23/83) in the DM group, 30.0% (9/30) in the HT group, 50.0% (6/12) in MD group, and 70.6% (12/17) in the HT + MD group. The rate in the HT + MD group was significantly higher than in that of the DM and HT groups (p less than 0.001, p less than 0.01). Blood pool scintigrams revealed that in the HT + MD group, as compared with the normal control group, both 1/3 FF and PFR were significantly depressed, in addition to significant TPF prolongation in the former (p less than 0.001, p less than 0.05, p less than 0.05). These findings suggest that in diabetic patients hypertension and myocardial damage would lead to a high incidence of abnormality in SPECT and left ventricular rapid filling dysfunction. This indicate a high incidence of latent cardiac disease which can be recognized in diabetic patients by stress myocardial and blood pool scintigrams.