The clinical, biochemical, and histological features of 27 children with syndromic paucity of the interlobular bile ducts are described. All presented in the first 5 months of life, 21 with jaundice, two with spontaneous bleeding due to vitamin K malabsorption in addition to jaundice, two with pruritus, and two with failure to thrive. Interlobular bile ducts were abundant in liver biopsies from five (18% of cases) in the first 6 months of life. The degree of portal fibrosis and cellular infiltrate was mild in all except three patients. Clinically significant heart lesions occurred in 52% but only 22% had peripheral pulmonary stenosis. Characteristic facial appearances were present in only 70%; embryotoxon and vertebral anomalies were present in 56 and 33%, respectively. Two infants died of cardiovascular complications, one of alimentary bleeding and one of progressive liver disease. Complications of vitamin K deficiency occurred in 15%, vitamin D deficiency in 30%, and vitamin E deficiency in 37%. Survivors at ages of 19 months to 16.5 years had considerable morbidity with pruritus occurring in 70%, jaundice in 48%, xanthomas in 30%, 74% having hepatomegaly and 63% splenomegaly. All had abnormal biochemical tests of liver function, 90% had growth retardation, and 50% developmental delay. We conclude that differentiation from extrahepatic biliary atresia can be difficult if biliary flow cannot be demonstrated. Prevention of fat-soluble vitamin deficiency is essential. Further research is required to decrease the morbidity associated with this syndrome in infancy.