The effect of increased extracorporeal blood flow rate on left ventricular (LV) function has been studied during volume-controlled bicarbonate hemodialysis. Ten stable patients on chronic hemodialysis, with a mean age of 28 years (range 19-38) were studied using two-dimensional and Doppler echocardiography. The mean time on hemodialysis was 32 months (range 3-60). All patients were investigated during three dialysis sessions on the first day of the week for 3 consecutive weeks. The blood flow rate was chosen randomly as 250, 350, or 450 cc/min. Apart from the time of hemodialysis and blood flow rate, other parameters of the hemodialysis were kept stable during all three sessions. Echocardiographic studies were done before, at mid dialysis, and during the last 15 min of each dialysis session. The following parameters were evaluated: heart rate, mean blood pressure, shortening fraction, ejection fraction, cardiac output, and pre-ejection period/LV ejection time ratio. The changes of the measured cardiac parameters at the beginning, middle and end of each session were not significantly different. Furthermore, the differences in changes between the three different sessions were comparable. Our results indicate that an increase in dialysis blood flow rate up to 450 cc/min does not have an adverse effect on the left ventricle in patients on maintenance hemodialysis and with stable cardiovascular function.