Two brothers had repeated episodes of vomiting, hepatomegaly, and laboratory evidence of deranged liver function. Eight years after the onset of illness in one patient, and 1½ years in the second, they each died in hepatic coma, at the ages of 14 and 16 years, respectively. Results of a liver biopsy examination performed in the older brother during an asymptomatic interval were normal. Autopsy, performed only on the younger brother, showed fatty infiltration of the liver and kidneys. No cause could be determined for this entity.