Isolated rat livers were perfused with a haemoglobin-free Krebs-Ringer solution containing 35 g albumin/1. During a 3 hour perfusion total flow, O2-uptake rate and local O2-supply remained constant. During the same period of time the ATP-content increased from a value of 0.59 +/- 0.17 mumol/g to 1.81 +/- 0.42 mumol/g. The low initial value was due to the ischaemic period during preparation of the organ. The glycogen content increased by 13.4 mg/g, indicating that the organ did not lose the ability for glyconeogenesis. In addition to an increase in glycogen, there was a continuous increase in the glucose concentration of the perfusate, while lactate was taken up by the organ. The results indicate that the isolated organ can be perfused for at least 3 hours without development of disturbances in local O2-supply.