For the assessment of graft viability, serum hyaluronic acid (HA) levels during porcine orthotopic liver transplantation were measured in two groups: group 1 (viable: n = 5) in which allografts were transplanted following a minimal cold (4 degrees C) preservation, and group 2 (nonviable: n = 4) in which allografts were transplanted after cold static storage (4 degrees C) for 24 h in University of Wisconsin solution. The changes in the HA levels reached a significant difference between the two groups at 30 min after reperfusion (P < 0.02). In group 1, all animals survived for over 4 days, while all animals in group 2 died within 24 h. The serum HA also demonstrated a significant correlation with prothrombin time, beta-glucuronidase, and aspartate aminotransferase at 120 min after reperfusion. These results suggest that the measurement of serum HA is a potentially effective index for evaluating hepatic allograft viability.