The differential diagnosis of infants with prolonged obstructive jaundice is usually puzzling and often in error.1The differentiation between obstruction to the outflow of bile on the basis of hepatocellular disease and that due to atresia of the extrahepatic bile ducts is made difficult by a variety of factors. Among these are the frequency with which hepatitis leads to prolonged, essentially complete obstruction to the outflow of bile into the intestinal tract,2,3the poor correlation between the results of the commonly used tests for hepatic parenchymal cell damage (flocculation, turbidity1and transaminase tests5), and the disease process affecting the patient. The unreliability of histories concerning the time of onset of jaundice and the character of stool color,1as well as the results of chemical tests for bile pigments in urine and stool, may also lead to error in diagnosis.1,4 These facts have been more