During a period of 7 years the case histories of 60 infants with direct hyperbilirubinaemia were prospectively evaluated. At presentation the majority of infants had an age below 1 month. By close clinical follow-up of all infants including the observation of acholic stools (21 infants), quantitative estimations of lipoprotein X during cholestyramine therapy (17 infants), cholescintigraphy (20 infants) and percutaneous liver biopsy (17 infants) the efficiency of the preoperative diagnostic work-up reached 96.6%. Liver biopsies were carried out selectively in only 29.3% of all infants (47.6% in infants with acholic stools and 17.9% in infants with normal stools); their efficiency in the differential diagnosis of extrahepatic biliary atresia was 88.2%.