Five infants, three dying neonatally and two later in the first year of life, had renal, hepatic, and pancreatic dysplasia, a combination of abnormalities first described by Ivemark et al [1959]. The renal malformation consisted of cystic dysplasia, with abnormally differentiated ducts, deficient nephron differentiation, and glomerular cysts. The hepatic abnormality consisted of enlarged portal areas containing numerous elongated biliary "profiles," with a tendency to perilobular fibrosis. Serial liver biopsies in one child with cholestasis from birth showed a progression from bile duct paucity at 1 1/2 wk to typical biliary "dysgenesis" at 7 mo. Four of the five children had intrahepatic ductal dilatation, diagnosed ante mortem in the two older children as Caroli disease. The pancreatic abnormality consisted of fibrosis and cysts, with a diminution of parenchymal tissue. The clinical and functional reflection of these abnormalities in the two children surviving the newborn period included renal insufficiency, chronic jaundice, and insulin-dependent diabetes mellitus. Similar renal, hepatic, and pancreatic abnormalities occur in other syndromes, including trisomy 9, Meckel syndrome, Jeune, Saldino-Noonan, and Elejalde types of chondrodysplasia, and glutaric aciduria II. After exclusion of identifiable syndromes, the remaining cases of renal-hepatic-pancreatic dysplasia do not necessarily constitute a homogeneous group.