The elimination rate of a parenteral dose of galactose, an indirect indication of the redox state of the liver hepatocytes, was determined in 46 children during anaesthesia and surgery. The anaesthetics used were thiopentone sodium, propanidid, halothane, diethyl ether, and nitrous oxide, administered in seven different combinations. The results suggest no direct involvement by any of the types of anaesthesia used in the liver redox system. Nevertheless, the normal oxidative metabolism may be affected indirectly by thiopentone-halothane combinations, unless an adequate alveolar ventilation is provided by appropriate measures.