Dopamine is administered frequently in the operating theatre and intensive care unit patients undergoing mechanical ventilation with the aim of specifically enhancing renal blood flow. In an uncontrolled, open study, we administered sequentially different doses of dopamine (0, 2, 4, 8 and 0 μg kg -1 min -1 ) during a 1-h period each. Systemic haemodynamic and renal haemodynamic variables were measured simultaneously using a pulmonary artery catheter and radiopharmaceuticals, respectively. We studied seven haemodynamically stable patients (mean age 66 yr), with a serum creatinine concentration < 160 μmol litre -1 , after elective infrarenal abdominal aortic reconstruction. All patients received extradural analgesia with bupivacaine and sufentanil, and none had a previous history of heart failure. Dopamine induced a dose-dependent increase in cardiac index which returned to baseline after cessation of the dopamine infusion. Glomerular filtration rate (GFR) increased with all doses of dopamine, whereas renal blood flow (RBF) increased significantly only with the 2- and 4-μg kg -1 min -1 doses. However, the ratio RBF/cardiac output remained unchanged with the 2- and 4-μg kg -1 min -1 doses, but decreased with 8 μg kg -1 min -1 from 14 (1.5)% to 10 (1.3)%. We conclude that dopamine increased RBF and GFR as a result of an increase in cardiac output.