The aim of this study was to describe biochemical and liver function test changes after hepatectomy in 33 patients with the following characteristics: absence of underlying liver disease, no blood or plasma transfusion during the perioperative period, uneventful postoperative course. Resection with a temporary pedicle inflow occlusion (10-45 min) consisted of unisegmentectomy or less in 15 patients and bisegmentectomy or more in 18. Blood tests showed: a correlation between aminotransferase rise and duration of ischaemia, and a fall in prothrombin time and factor V levels correlating with the weight of resected specimen at day 1; a moderate gamma-glutamyl transpeptidase and alkaline phosphatase elevation and a rise in fibrinogen level correlating with the extent of resection at day 7. Changes in haemoglobin level, white cell count, platelet count, prothrombin time, factor V level and serum bilirubin level tended to return to preoperative levels by day 7. For gamma-glutamyl transpeptidase and alkaline phosphatase, increased levels persisted for 8-12 weeks after resection. These results, in this selected group of patients, allow a description of the 'natural history' of hepatectomy. The knowledge of these 'natural' changes may contribute to the early detection of postoperative complications.