Hypertension is the most common complication of r-HuEPO therapy in dialysis patients. The aim of this study was to test the hypothesis that hypertension develops in patients who fail to autoregulate adequately their hemodynamic response to correction of anemia. Twenty-five dialysis patients (17-71 yrs, 13 male, 13 CAPD) initially received r-HuEPO 50 U/kg 3 times/week intravenously or subcutaneously. Hypertension, defined as a rise in mean blood pressure (BP) of greater than 15 mmHg during therapy developed in 44% (Group 1: stable BP; Group 2: rise in BP). There was no difference in sex, age, mode of dialysis or route of administration of r-HuEPO between the groups. Before commencement and after 6-12 months of r-HuEPO therapy, assessment of the baroreflex arc was performed using the Valsalva ratio and orthostatic BP testing, sympathetic efferent nerve function was assessed by the cold pressor test and afferent parasympathetic function by the 30:15 ratio and heart rate variation (HRV). No difference was detected prior to r-HuEPO therapy between the two groups in Valsalva ratio (Group 1: 1.26 +/- 0.06 vs Group 2: 1.23 +/- 0.06, mean +/- SEM); 30:15 ratio (1.06 +/- 0.02 vs 1.03 +/- 0.01), or systolic, diastolic, mean BP or pulse rate after standing for 3 minutes or following hand immersion in ice slush. Both groups had a fall in systolic and diastolic BP (p < 0.05) and a rise in pulse rate (p < 0.05) on standing. HRV during deep respiration between the 2 groups was not different (9.6 +/- 2.3 vs 7.1 +/- 1.4 beats/minute).(ABSTRACT TRUNCATED AT 250 WORDS)