Plasma norepinephrine (NE), epinephrine (EPI), dopamine (DPM), dopamine β-hydroxylase (DBH), and renin were measured in patients undergoing maintenance hemodialysis. The predialysis NE, EPI and DPM concentrations were lower than normal at 29, 7.3 and 4.8 pg/ml, respectively. The NE level increased in the erect posture to 100 pg/ml at 30 min. Levels were also measured during the postdialysis period, and were approximately the same as in normal subjects, but lower than previously published values for patients undergoing hemodialysis. In the predialysis period, NE and renin correlated upon assumption of the upright posture. It is concluded that maintenance hemodialysis can be carried out without a major distortion of the plasma catecholamine levels