The relationship of left ventricular (LV) filling to the clinical and echocardiographic characteristics of 51 patients with untreated hypertension (borderline hypertension n = 17, essential hypertension n = 34) was investigated using two-dimensional echocardiography and Doppler ultrasound. Twenty-five patients had evidence of abnormal LV filling. Linear regression analysis revealed weak but significant correlations of LV filling with age (r = -0.53; P less than 0.0001), systolic blood pressure (r = -0.38; P less than 0.006), LV septal wall thickness (r = -0.44; P less than 0.0001) and LV mass index (r = -0.33; P less than 0.02). There was no association between LV filling and sex, race, heart rate or LV posterior wall thickness or cavity dimension. After stepwise regression analysis, age was found to be the only independent variable associated with LV filling, indicating that the other variables were dependent on age. This study suggests that a) abnormal LV filling is a frequent observation in hypertension b) LV filling is more dependent on age than blood pressure or LV size and c) other pathophysiological factors, so far undetermined, must contribute to the development of these abnormalities.