The gamma-GT/ASAT (aspartate aminotransferase) and gamma-GT/ALAT (alanine aminotransferase) ratios were examined in 6 children with neonatal hepatitis (NH), 14 children with extrahepatic biliary atresia (EHBA), and 8 children with intrahepatic cholestasis (IHC) (of which 3 with the Aagenaes syndrome). A ratio above 1 is suggestive of EHBA. Both ratios differentiate very well between NH and EHBA, but there is considerable overlap in the enzyme ratios between the EHBA and the IHC groups. Gamma-GT/transaminase ratios may prove to be a useful indicator in the diagnostic work-up of children with liver and biliary tract disease, allowing for early surgery in patients with EHBA, and with a low risk of subjecting NH patients to unnecessary surgery. In our cases the gamma-GT/ALAT ratio separated better between EHBA and IHC than the gamma-GT/ASAT ratio. Furthermore, the case histories made EHBA seem unlikely in two out of three IHC patients with a gamma-GT/ALAT ratio above 1.