Effects of Allolobophora caliginosatrapezoides (Ac) polysaccharide fractions on the inflammation and hypersensitivity were studied in vivo. It showed that Ac polysaccharide fractions have the significant inhibitory activities of inflammation and hypersensitivity; They inhibited significantly the carrageenin-induced paw edema and acetic acid-induced writhing syndrome. They also inhibited significantly the Arthus reaction and delayed hypersensitivity in the sheep red blood cell-sensitized mice in accordance with the inhibition of haemaglutinin titer, haemolysin titer, plaque-forming cells and rosette-forming cells. They also improved markedly the oxazolone-induced dermatitis in rats dose-dependently. As the above results, it exhibited that Ac polysaccharide fraction inhibited not only humoral immune response, but also cell-mediated immune response. It seemed that methanol and ether extracts have also another physiological active agents.