Development of new assays for accurate quantification of bile pigments in plasma have facilitated their clinical application. Hyperbilirubinemia and jaundice occur frequently in the neonatal period. The purpose of the present study was to determine reference intervals for bilirubins in 60 fullterm healthy infants during the first four days of life. For comparison the bilirubin fractions were analyzed in an infant with biliary atresia and six adults with hepatobiliary disorders.