Vasopressin has been found to impair hepatic function in patients with cirrhosis. The aim of this study was to investigate whether oxygen inhalation could improve hepatic function during vasopressin infusion. Vasopressin (0.3 iu/min) was infused into eight patients with cirrhosis for 50 min. During the first 30 min they were ventilated by room air and for the following 20 min by oxygen (approximate 50% of FiO2). The extra oxygen inhalation caused a typical increase in arterial (+7%, P less than 0.01), portal venous (+8%, P less than 0.05), and hepatic venous (+9%, P less than 0.01) oxygen content. No effect was noted in arterio-hepatic venous and portal venous-hepatic venous oxygen content difference in comparison with the values after vasopressin alone. The hepatic perfusion remained unchanged. These results suggest that the extra oxygen did not increase hepatic oxygen uptake. Similarly, intrinsic clearance of indocyanine green did not improve. It is concluded that oxygen supplement in this setting has no hepatic benefit in patients with cirrhosis.