The subject of cystic disease of the liver and kidneys has been reviewed. A family has been studied in which at least four and probably six of seven children of normal parents have been affected by the disease, as shown by clinical study and biopsy, liver function and biopsy, and by pyelograms made after intravenous injection of radio-opaque material. The prognosis of the condition usually depends upon the amount of renal involvement. In the patients studied here, however, the disease process in the liver has assumed even greater clinical importance, since two children have developed severe portal hypertension.