Certain highly purified forms of rat lysosomal glycosidases, β glucuronidase and N acetyl β D glucosaminidase, are rapidly cleared from the circulation following intravenous infusion. Several lines of evidence are presented which indicate that the primary site of enzyme uptake is the liver. Clearance of the 2 enzymes was unaffected by nephrectomy, whereas it was abolished by evisceration. Tissue distribution experiments with native and [125I] β glucuronidase indicate the liver as the major, if not exclusive, site of enzyme uptake. Experiments with the isolated perfused liver showed clearance of certain enzyme preparations but not others. Those enzymes cleared by the isolated perfused liver were likewise cleared in vivo. Liver fractionation studies following infusion of large doses of β glucuronidase revealed a rapid, short lived increase in microsomal β glucuronidase and a slower but larger increase in lysosomal β glucuronidase. The results indicate that β glucuronidase, N acetyl β D glucosaminidase, and probably other glycosidases are rapidly incorporated into the lysosomal compartment of liver.