To determine whether the blood lidocaine level during the continuous epidural block correlates with the preoperative liver function, i.e. serum albumin level, serum cholinesterase (ChE) activity, glutamic pyruvic transaminase (GPT) and indocyanine green retention rate (ICG R15), we measured the arterial serum lidocaine level in 45 abdominal surgical patients. The epidural catheter was advanced cephalad from Th10-L2 interspace, for a distance of 4 to 5 cm. Anesthesia was induced with thiopental, and maintained with continuous epidural block plus N2O, O2 and low concentration of isoflurane inhalation. We started epidural block with 0.3 ml.kg-1 body weight of 1.5% lidocaine and added half of the initial dose every 30 minutes for 2 hours. Serum lidocaine concentration was measured every 15 minutes after the lidocaine injection into epidural space. The result revealed that the lower the serum albumin level and ChE activity were, the higher the serum lidocaine level was and, that it had no significant correlation with GPT and ICG R15. We conclude that any patient with hypoalbuminemia and low serum ChE activity might have higher blood lidocaine levels during the continuous epidural block.