Lipid droplets surrounded by a peripheral membrane closely apposed to an electron-dense layer and containing acid phosphatase activity, similar to the lipolysosomes in hamsters described by Nehemiah and Novikoff (J. Cell Biol. 59: 246a, 1973; Exp. Mol. Pathol. 21:398, 1974), were found in the hepatocytes of patients with Wilson's disease. These organelles account for 1 to 2 per cent of the observed lipid droplets at the stage of the disease when excess fat is present. The occurrence of lipolysosomes in a condition not known to be associated with an acid lipase deficiency suggests that lipolysosomes may represent a nonspecific, alternate route for the mobilization of excess lipid from hepatocytes.