The glucuronic acid analogue of 1-deoxynojirimycin, 2(S)-carboxy-3(R), 4(R), 5(S)-trihydroxypiperidine, recently isolated from seeds of Baphia racemosa, is a novel specific inhibitor of human liver beta-D-glucuronidase and alpha-L-iduronidase. No other glycosidases are inhibited. The inhibition of beta-D-glucuronidase is competitive, with a Ki of 8 X 10(-5) M and is pH-dependent. This inhibitor may be useful to induce a mucopolysaccharidosis or to investigate the function of microsomal beta-D-glucuronidase.