Cerebroside sulfatase (CSase) activator was isolated from human liver by acetone precipitation, anion-exchange chromatography, gel filtration and polyacrylamide gel electrophoresis. The CSase activator was a heat-stable protein with an isoelectric point of 4.54. Molecular weight (Mr) of the activator was estimated as 22,000 with the gel permeation and about 8,000 by gel electrophoresis in the presence of sodium dodecyl sulfate, suggesting that the native activator is a trimer of a subunit with Mr 8,000. The CSase activator formed a complex with an equimolar amount of cerebroside sulfate (CS), when examined by gel permeation experiments. The activator also bound to galactosylceramide and GM2 ganglioside but scarcely to GM1 ganglioside, and activated to some extent beta-N-acetyl-hexosaminidase A and beta-galactosidase, although the CSase activator could be clearly distinguished from the GM1 beta-galactosidase activator so far known. Though the affinity chromatography using glycolipid ligands, the CSase activator did not recognize sulfate group of CS, but appeared to have a relatively broad specificity for lipid-linked hexose.