Morphometric analysis of the liver lesions in patients with various forms of cystic disease of the liver in childhood demonstrates that the entities called the congenital, perinatal, and infantile forms of polycystic disease produce the same liver lesion. The data suggest that these entities are actually the same disorder, for which the name infantile polycystic disease (of the liver and kidneys) is recommended. In all patients with this autosomal recessive disorder there is involvement of both the liver and the kidneys, and patients present with hepatonephromegaly at birth or in early infancy. Similarly, the entity called the juvenile form of polycystic disease produces the same liver lesion as does the disease to which the term congenital hepatic fibrosis has been applied to describe patients presenting in later childhood with portal hypertension. The latter name is recommended to distinguish this condition from infantile polycystic disease. Nephromegaly is not a feature of this also autosomal recessive disease, but renal insufficiency, progressing slowly through later childhood and adolescence, is. The hepatic lesions of infantile polycystic disease and congenital hepatic fibrosis differ from those of other disorders causing cystic lesions of the liver and kidneys, either regularly (Meckel's syndrome, Jeune's syndrome) or variably (vaginal atresia syndrome, tuberous sclerosis, medullary cystic disease).