Blood pressure as well as noradrenaline, creatinine and electrolytes in blood and urine were compared in normal controls (n = 25), patients with chronic renal failure (n = 39), patients with continuous ambulatory peritoneal dialysis (CAPD) (n = 28) and haemodialysis patients before and after renal transplantation (n = 63). The average blood pressures of the control group and the CAPD patients were lower than those of the renal failure patients without and with haemodialysis. After renal transplantation elevated blood pressure normalised in 18% within the following 6 months. In all groups of patients with renal failure the mean noradrenaline plasma concentration was increased more than three-fold of normal values: 1,470 pg/ml in patients with chronic renal failure, 1,366 pg/ml in CAPD patients and 1,284 pg/ml in patients with haemodialysis. No correlation was found between these elevated noradrenaline plasma levels and blood pressure. However, there was a significant correlation between noradrenaline excretion and sodium excretion. Compared to the controls, the urine excretion of noradrenaline was significantly lower in patients with chronic renal failure and almost zero in patients with dialysis treatment. Two days after renal transplantation the mean noradrenaline urine excretion increased to 15.7 +/- 1.8 micrograms/day and 4 days after transplantation the noradrenaline plasma concentration decreased to 592 +/- 155 pg/ml. Nine months after renal transplantation the creatinine clearance was 76 ml/min and the mean noradrenaline plasma concentration 438 +/- 153 pg/ml. It is concluded that in chronic renal failure the level of noradrenaline plasma concentration is dependent on renal function.