β-Glucuronidase was purified from rat uter us by (NH₄)₂SO₄ fractionation, DEAE-cellulose chromatography, gel filtration on Sephadex G-200, CM-cellulose chromatography, and affinity chromatography on Concanavalin-A Sepharose. The purified enzyme appeares homogeneous on electrophoresis in a 7.5 % polyacrylamide gel at pH 8.3, and had a molecular weight of 288,000 daltons by gel filtration. SDS polyacrylamide gel electrophoresis indicated that enzyme consisted of subunit with molecular weight of 75, 000. The pH profile of the enyzme varied when changing substrate concentration and ionic strength. The enzyme was more stable at high temperature in acidic buffers than in neutral ones. The Km value for p-nitrophenyl-β-D-glucuronide as substrate was 0. 25 mM, and the enzyme was inhibited by heavy metal ions, such as Hg^(2+), Cu^(2+) and Ag^+. Citrate, heparin, and acetate also inhibited the enzeme. Various salts decrease the enzyme activity by 20 % at ionic strength of 0.4.