Changes in systemic, hepatosplanchnic and femoral blood flow and liver function after cardiac surgery were studied in 17 patients from April to October 1995. Blood flows were measured every 3 h and gastric mucosal PCO2 (by tonometry) every hour from arrival in the intensive care unit until extubation. Cardiac output and systemic oxygen consumption increased from 2.83 (0.68) litres min-1 m-2 to 3.17 (0.57) litres min-1 m-2 and from 126 (18) ml min-1 m-2 to 135 (44) ml min-1 m-2, respectively (mean (SD), P = 0.028 and P = 0.019, respectively, baseline vs 6 h). The fraction of cardiac output distributed to the splanchnic region decreased from 0.25 (0.06) to 0.20 (0.04) (P = 0.004) while splanchnic oxygen extraction increased from 0.43 (0.15) to 0.50 (0.12) (P = 0.019). Femoral blood flow increased from 0.18 (0.07) litres min-1 m-2 to 0.23 (0.09) litres min-1 m-2, (P = 0.006, baseline vs 3 h) but femoral oxygen consumption did not change. Changes in blood flow were not reflected by venous-arterial PCO2 gradients. Initially high glutathione transferase alpha concentrations decreased and indocyanine green extraction was well preserved. We conclude that the predominant increase in peripheral blood flow and the increased oxygen uptake in certain regions of the body may increase the risk of a mismatch between splanchnic perfusion and metabolic demands. This mismatch was not associated with impaired liver function or cellular integrity.