Subclinical myocardial dysfunction occurs in a significant number of patients with type 2 diabetes (DM). Assessment of ventricular long-axis function by measuring mitral annular velocities using tissue Doppler echocardiography (TDE) is thought to provide a more sensitive index of systolic and diastolic function. The purpose of this study was to evaluate ventricular long axis function at rest and during exercise in patients with DM without overt heart disease. Mitral annular systolic (S���) and early diastolic (E���) velocities were measured at rest and during supine bicycle exercise (25W, 3 minutes increments) in 60 patients (30 male, mean age 54 years) with DM and 52 patients (19 male) with age-matched control. There were no significant differences in mitral inflow and annular velocities between the groups at rest. However, S��� during exercise (8.2+/-1.8 vs 9.2+/-2.1 cm/s at 50 W, p=0.0015) and the magnitude of change of E��� (3.0+/-1.9 vs 4.0+/-2.5 cm/s from base to 50W, p=0.03) and S��� with exercise (0.6+/-1.2 vs 1.5+/-1.7 cm/s from base to 25W, p=0.0012; 1.3+/-1.5 vs 2.6+/-1.7 cm/s from base to 50W, p=0.0003) was significantly lower in patients with DM compared with control. In conclusion, unlike resting measurement of mitral inflow and annular velocities, changes of E' and S' during exercise were significantly different and abnormal in patients with DM. The assessment of LV longitudinal functional reserve with exercise using TDE would be better to detect early myocardial dysfunction in patients with DM.