Cardiac function was measured in 10 children (mean age 12 years) undergoing chronic intermittent hemodialysis. Blood pressure, heart rate and body weight were checked three times before and after hemodialysis. Echocardiographic studies were performed according to the references of the American society of echocardiography. 6 patients were normotensive, 4 patients hypertensive. Cardiac function was normal before and after hemodialysis in all patients. Ultrafiltration reduced body weight on average by 1.2 kg. The mean systolic blood pressure remained unchanged, the mean diastolic blood pressure declined in normotensive patients from 66 mm Hg to 53 mm Hg and in hypertensive patients from 100 to 85 mm Hg on average; the systolic leftventricular diameter (LVES) was reduced by dialysis from 2.7 to 2.3 cm, the enddiastolic leftventricular diameter (LVED) from 4.42 to 4.02. Cardiac output declined from 62.04 ml to 56.68 ml/min, whereas heart rate, shortening fraction and mean circumferential fiber-shortening-time increased. In normotensive patients LVED shortened more (4.4 to 3.86 cm) than in hypertensive children (4.44 to cardiac output 4.18 cm), but there were no significant differences. Significantly decreased only in the normotensive children. In hypertensive children the shortening fraction increased significantly (35.54 to 42.48%) in contrast to normotensive children (40.84 to 38.44%). Cardiac preload (LVES) and (LVED) and afterload (diastolic pressure) was reduced significantly after volume elimination. These changes in cardiac function suggest, that cardiac alterations found before hemodialysis are only functional and not structural.