A study of the clearance of liver lysosomal enzymes was carried out in the rat. Purified rat liver lysosomal β D glucuronidase (EC 220.127.116.11), N acetyl β D glucosaminidase (EC 18.104.22.168), α L fucosidase (EC 22.214.171.124), and α D mannosidase (EC 126.96.36.199), as well as rat preputial gland β glucuronidase, were infused intravenously into anesthetized rats. All of the enzymes were rapidly cleared from the circulation. Sodium periodate oxidation of lysosomal β glucuronidase resulted in a near abolition of rapid clearance, a reduction in concanavalin A Sepharose binding, and a reduction in neutral sugar content, accompanied by alteration in isoelectric focusing properties. Similarly, periodate oxidation of lysosomal N acetyl β D glucosaminidase resulted in a loss of the rapid clearance property. These results suggest that specific recognition sites occur on lysosomal hydrolases which mediate clearance following intravenous injection, and that these sites involve the carbohydrate portions of the enzymes.