BACKGROUND: Early recognition of heart disease in diabetics is a highly desirable goal, and diastolic dysfunction, one of its earliest manifestations, can be readily assessed by tissue Doppler imaging. We tested in normotensive diabetics without signs of coronary artery disease whether tissue Doppler imaging would improve the diagnosis of diastolic dysfunction beyond classical criteria and identify patients already presenting impaired cardiac performance. METHODS: We studied 79 patients (56 males, 55 type-2 diabetes mellitus) who underwent Doppler echocardiography, and exercise testing. Diastolic dysfunction was diagnosed either based on European Study Group on Diastolic Heart Failure guidelines or by tissue Doppler imaging provided that both of the following criteria were met: Em/Am ratio <1; and Em < 8.5 cm/sec. RESULTS: Tissue Doppler imaging identified diastolic dysfunction in 26.6% of diabetics, while classical criteria did so in 40.5% of the cases. The group identified by classical criteria did not differ significantly from patients without diastolic dysfunction, while in the group identified by Tissue Doppler imaging, significant differences were highlighted, including worse exercise tolerance and higher left ventricular mass index. Moreover, in multiple regression analysis, Em myocardial velocity and body mass index were the only variables independently related to exercise tolerance. CONCLUSION: Differently from classical criteria based on pulsed Doppler, Tissue Doppler imaging identifies a group of asymptomatic normotensive diabetics with diastolic dysfunction and reduced exercise tolerance. Confirmation of the prognostic importance of our findings could justify the use of Tissue Doppler imaging for diastolic function assessment in diabetics with otherwise healthy hearts.