Aims: Patients with type 2 diabetes mellitus (DM) often suffer disproportionately and have a worse outcome when burdened with cardiovascular complications compared with those without DM. A specific heart muscle disease reportedly caused by DM per se may explain this. We sought to investigate whether an echo Doppler diagnosis of such a myocardial disease is clinically relevant in DM with or without coexistent coronary artery disease (CAD) and/or hypertension (HTN). Subjects and Methods: Two hundred subjects (127 males, 73 females, 56 ± 10 years) including controls (n = 23), patients with HTN (n = 20), CAD (n = 35), uncomplicated DM (n = 59), DM+HTN (n = 27), DM+CAD (n = 16) and DM+CAD+HTN (n = 20) underwent tissue Doppler-enhanced dobutamine stress echocardiography. Myocardial function was assessed by measuring left ventricular myocardial peak systolic velocity (PSV) and early diastolic velocity at rest and during peak stress, besides measurements of standard Doppler variables. Results: Average left ventricular PSV at rest was significantly lower in CAD (4.7 ± 1.5) compared with controls (5.7 ± 1.2) and in DM+CAD+HTN (4.6 ± 1.4) compared with DM (5.6 ± 1.3; all p < 0.05). During peak stress, lower PSV persisted in CAD (9.5 ± 3.1) and DM+CAD+HTN (8.1 ± 2.7), while appearing de novo in DM (11.3 ± 2.6) and HTN (11.0 ± 2.3) unlike in the controls (12.5 ± 2.5; all p < 0.001). When pooled together, DM subjects with CAD and/or HTN or both had significantly lower PSV (9.1 ± 2.7) than those without (10.0 ± 2.8; p < 0.001). Early diastolic velocity response was equally lower in both groups compared with the controls. Conclusion: The results suggest that dobutamine stress unmasks myocardial functional disturbances caused by uncomplicated DM. The discrete disturbances become quantitatively more pronounced in the presence of coexistent cardiovascular diseases.