Six patients on conventional acetate hemodialysis who had a marked decrease in total peripheral resistance index (TPRI) and hypotension after dialysis were selected for study. Systemic hemodynamic factors such as cardiac output, blood pressure, hematocrit and heart rate were measured, and the values were compared to those found after bicarbonate hemodialysis (Bi-HD) or ultrafiltration without simultaneous dialysis (UF) in the same patients. After Bi-HD and UF, the hemodynamic indices remained stable. Hematocrit level was significantly elevated after Bi-HD (+2.7%, P less than 0.05). Heart rate was insignificantly increased after each procedure. We concluded that Bi-HD can prevent unpleasant side effects induced by the decrease in TPRI with acetate hemodialysis. The stability of TPRI resulting from the increase in hematocrit level during Bi-HD may contribute to the prevention of cardiovascular instability.