Although hyperlactemia is known to accompany hepatic failure and metabolic acidosis, few reports examined the relationships between lactate concentrations and outcome after liver resection. We examined the ability of arterial plasma lactate concentration to predict the patient outcome after hepatectomy. The relationships of arterial lactate and base excess (BE) measured on admission to the intensive care unit (ICU) after hepatectomy to postoperative outcome were investigated in 151 consecutive patients. Lactate level was significantly higher in nonsurvivors than in survivors (P < 0.001), and in patients with postoperative complications than in those without complications (P < 0.001). Base excess was significantly reduced in nonsurvivors (P < 0.001) and in patients with postoperative complications (P = 0.004). The area under the receiver-operator curve of lactate to mortality was 0.86, whereas that of BE to the mortality was 0.82. Moderate correlation was observed between the lactate level at ICU admission and the highest total bilirubin concentration measured within 14 days after the surgery (r = 0.61), whereas the correlation between BE and bilirubin levels was lower (r = 0.35). Using multivariate analysis, the lactate level independently predicted mortality (P = 0.008) and morbidity (P = 0.013). Lactate (P < 0.001) and BE (P = 0.0068) levels both independently predicted the highest bilirubin concentration. The arterial plasma lactate concentration measured on admission to ICU seemed an excellent predictor of patient outcome after liver resection.