Purpose: The aim of this study was to clarify whether serum hyaluronic acid level (SHA) can reflect the degree of liver fibrosis in biliary atresia (BA). Methods: SHA was measured in 44 postoperative BA patients at 7 months to 22 years of age, with sandwich enzyme method (Hy-A 100 kit). SHA was compared with T.Bil (group 1,T Sil < 2; group 2, 2 <less than or equal to> Bil T < 5; group 3, T Bil <greater than or equal to> 5 mg/dL), fibrosis score (0-6, the number of abnormal values among Alb, PT, ChE, T Chol, Fischer's ratio, prealbumin), and histologic grading (0-IV). Results: SHA was 499.8 +/- 332.5 in group 3, significantly higher than in the control, group 1, or group 2. As fibrosis score rose, SHA became higher, and SHA in Score 6 (430.1 +/- 366.1 ng/mL) and score-5 (172.9 +/- 141.8 ng/mL) was significantly higher than in the control and other scores, respectively. As the histologic grade rose, SHA became higher, and SHA in grade IV (444.8 +/- 323.5 ng/mL) and grade III (166.0 +/- 70.3 ng/mL) was significantly higher than in the control or other Grades. Serial change of SHA since before HPE was parallel to the clinical course in 8 patients. Conclusion: SHA may be a useful serum marker reflecting the degree of liver fibrosis in BA. Copyright (C) 2000 by W.B. Saunders Company.