Purpose of the study was to evaluate the influence of different clinical and echocardiographic parameters on left ventricular diastolic filling in a group of 66 mild to moderate hypertensive subjects (mean age = 45.9 +/- 13.9 yrs) and in 49 normotensive controls (mean age = 44.2 +/- 15.9 yrs). All subjects underwent an echocardiographic study with pulsed Doppler evaluation of left ventricular filling. In the hypertensives, a noninvasive 24-hour blood pressure monitoring was performed. The ratio of early to atrial peak diastolic filling velocity (VmaxE/VmaxA) and the ratio between the respective velocity flow integral (Earea/Aarea) were significantly lower in the hypertensives compared to the normotensives (p less than 0.001). As within the hypertensives, office systolic blood pressure, average 24-hour mean blood pressure (24MBP), left atrial dimensions, and left ventricular mass index (MAXIND) were related both to age and diastolic filling. To study the relation between these parameters and diastolic filling a partial correlation test was used. The only variable related to diastolic filling, independently of age, was 24MBP (VmaxE/VmaxA vs 24MBP: r = -0.307, p less than 0.05, Earea/Aarea vs 24MBP: r = -0.261, p less than 0.05). Linear multivariate analysis using the method of stepwise regression established that age, 24MBP and heart rate were responsible for 75% of the VmaxE/VmaxA variance in the hypertensive group. To evaluate if the difference between the indexes of diastolic filling in the normotensives and the hypertensives varied according to age, we divided each group into two classes of subjects older and younger than 40 yrs. Under the age of 40 only VmaxE/VmaxA was significantly different in the two groups (p less than 0.05), while in the subjects older than 40 yrs both VmaxE/VmaxA and Earea/Aarea differed to a great level of statistical significance (p less than 0.001). The results of the present study allow the following conclusions: 1) age has the greatest influence on diastolic filling in both hypertensive and normotensive individuals. Diastolic filling is impaired in mild to moderate hypertension, when systolic function is still normal; 2) the worsening of diastolic filling determined by hypertension is more evident in the subjects greater than 40 yrs; 3) the only clinical variable that influences diastolic filling, independently of age, is 24MBP, while office blood pressure, MAXIND and left ventricular ejection fraction do not seem to be related to this clinical entity.