We investigated 25 patients (aged 20 to 70 yr) in septic shock with low systemic vascular resistance in order to assess the effects on renal function of prolonged (24 to 240 h) norepinephrine (NE) infusion (range 0.5 to 1.5 micrograms/kg.min). Two sets of renal function tests were made: a) control study before NE therapy after the initial intravascular loading and on dopamine infusion (mean dosage 14 +/- 2 micrograms/kg.min); b) in the last 24 h of NE infusion associated with dopamine (2 to 3 micrograms/kg.min). The following renal function tests were measured: urine flow rate, creatinine, osmolar and free water clearances, and fractional excretion of sodium (FENa). Data were collected only in 22 nonanuric patients: urine flow rate, creatinine, and osmolar clearance increased (p less than .001), and free water clearance (p less than .001) and FENa (p less than .02) decreased. These results suggest that NE (0.5 to 1.5 micrograms/kg.min) may be used in the treatment of human septic shock without deleterious renal effects.