In order to determine the accuracy of serum gamma-glutamyl transferase (GGT) as a test for biliary atresia, we reviewed the charts of 29 infants with cholestatic jaundice less than one year of age. All patients underwent liver biopsy or laparotomy with cholangiogram to establish neonatal hepatitis (NH) or extrahepatic biliary atresia (EHBA). We also gathered information from 176 patients from published studies. Sensitivity, specificity, and likelihood ratios (LR) were calculated with 95% confidence interval (95% CI). GGT levels of the EHBA group were higher than those from the NH group. For diagnosis of EHBA at a cut-off level >250 U/L, sensitivity was 83.3% (95% CI, 55.2- 95.3%); specificity, 70.6% (95 CI, 46.9-86.7%); and negative LR, <2.0. When we added data from other studies considering age (<4 weeks, 4-8 weeks, and >8 weeks), GGT performance increased, especially for the first age group: with cut-off of 150 U/L, sensitivity was 91.7%; specificity, 88%; and positive LR, 7.8. Thus, for improving reliability of GGT levels for EHBA diagnosis, they need to be correlated to infant age.