Left ventricular diastolic filling by Doppler echocardiography was investigated in 84 diabetic patients without evidence of heart disease and in 84 normotensive nondiabetic age- and sex-matched control subjects. Diabetic patients were subdivided into two groups on the basis of the presence of arterial hypertension. Group 1 comprised 41 normotensive diabetic patients (19 men, 22 women, mean age 63.7 +/- 9.1 years); Group 2 comprised 43 hypertensive diabetics (15 men, 28 women, mean age 65.6 +/- 9.6 years). Doppler measures of diastolic filling were significantly altered in the two groups as compared with control subjects. Peak atrial flow velocity, velocity integral for the atrial filling period, and atrial filling fraction were increased, whereas the ratio of peak early to peak atrial flow velocity and the ratio of flow velocity integrals were decreased, especially in Group 2 patients. Thirteen patients in Group 1 (32%) and 17 in Group 2 (40%) had evidence of diastolic dysfunction, as assessed by the presence of at least two independent abnormal indices (outside age-corrected 95% confidence interval). In each group, patients with altered diastolic filling differed slightly from diabetic patients with normal Doppler indices, tending to increased wall thickness and left ventricular mass. In conclusion, diastolic filling of the left ventricle is frequently altered in diabetic patients and is adversely affected by arterial hypertension whose coexistence further impairs left ventricular relaxation.