Two electrophoretically distinct components of glucuronidase have been resolved in extracts of murine liver. A mutation which results in a ten-fold reduction in liver glucuronidase activity leads to a reduction in intensity of both components. Since the substrate dependencies of both mutant (gg) and wild-type (GG) glucuronidase have previously been shown to be identical, it is suggested that the mutation results in a decreased concentration of liver glucuronidase molecules. Furthermore, the anodal electrophoretic component is shown to be preferentially localized in lysosomes, while the cathodal component is primarily microsomal. The difference in mobility of the two components may reflect a difference in membranous elements attached to the extracted glucuronidase molecule.