Abstract: A colorimetric method for determining the serum β-glucuronidase activity was reported. The mixture was incubated at 37℃ for 18 hr, the degree of hydrolysis of the substrate as a function of enzyme activity was determined by a Model 72 spectrophotometer at the wavelength of 560 nM. The mean serum enzyme activity of 91 healthy blood donors and volunteers was 378 + 142 U% (X±S.D.).The upper limitfor normal range was arbitrarily taken as 600U%. Serum β-glucuronidase activity was markedly increased in 29 patients with hepatic cancer, in which the mean serum enzyme activity was 984±592U%(X ± S.D.) and 22(76%)out of them were abnormal (p<0.001).