Subclinical left ventricular (LV) dysfunction may be identified by reduced longitudinal contraction. We sought to define the effects of subclinical LV dysfunction on radial contractility in 53 patients with diabetes mellitus with no LV hypertrophy, normal ejection fraction and no ischaemia as assessed by dobutamine echocardiography, in comparison with age-matched controls. Radial peak myocardial systolic velocity (Sm) and early diastolic velocity (Em), strain and strain rate were measured in the mid-posterior and mid-anteroseptal walls in parasternal views and each variable was averaged for individual patients (radial contractility). These variables were also measured in the mid-posterior and mid-anteroseptal walls in the apical long-axis view and each variable was averaged for individual patients (longitudinal contractility). Mean radial Sm, strain and strain rate were significantly increased in diabetic patients (2.9±0.6 cm/s, 28±5% and 1.8±0.4 s-1 respectively) compared with controls (2.4±0.7 cm/s, 23±4% and 1.6±0.3 s-1 respectively; all P<0.001), but there was no difference in Em (3.3±1.2 compared with 3.1±1.1 cm/s, P=not significant). In contrast, longitudinal Sm, Em, strain and strain rate were significantly lower in diabetic patients (3.6±1.1 cm/s, 4.3±1.6 cm/s, 21±4% and 1.6±0.3 s-1 respectively) than in controls (4.3±1.0 cm/s, 5.7±2.3 cm/s, 26±4% and 1.9±0.3 s-1 respectively; all P ⩽ 0.001). Thus radial contractility appears to compensate for reduced longitudinal contractility in subclinical LV dysfunction occurring in the absence of ischaemia or LV hypertrophy.