Radiostrontium is one of fallouts. It can be absorbed through intestine and causing radiation injury to bones. The purpose of this study is to evaluate the inhibitory effect of 10% chitosan (water soluble and insoluble) and 10% alginate (water soluble and insoluble) on radiostrontium adsorption. Water soluble and insoluble chitosans and alginates were given to 10 NIH male mice in each group for 7 days. At the 7th day, 74 MBq of 85Sr were given through orogastric tube. Chitosans and alginates were given for additional 7 days. During the 7 days, radioactivities of feces were counted daily. Finally animals were sacrificed, and radioactivities of bones were counted. Feca1 excretion was significantly higher in chitosan and alginate group as compared to control from the lst day (p〈0.01). Water soluble chitosan group showed highest fecal excretion. Bony retention was significantly lower in the treated group than the control (p〈0.01). There was no difference among treated groups. In conclusion, both water soluble and insoluble chitosans and alginates were effective agents on lowering orally ingested radiostrontium (85Sr)