To confirm therapeutic functionality of Urechis unicinctus which have been favored as a special seafood in Korea, the antitumor and immunological effect of those glycoprotein were studied. 4mg/kg dose of glycoprotein from Urechis unicinctus was most effective in solid tumor growth inhibition (43.63%) of sarcoma 180 cells. However, in case of mice injected with more than dose of 20mg/kg, tumor growth was not inhibited. The higher prolongation ratios were achieved at levels of 2mg/kg with 31.2% and 4mg/kg with 28.9%. The cytotoxic effect of glycoprotein on sarcoma 180 cells was increased slightly as administering level was increased. Number of total peritoneal exudate cells in all the glycoprotein administered groups increased remarkably meaning that Urechis unicinctus gly coprotein could help to improve immunity. Notable body weight change was not resulted in the glycoprotein treated mice compared with control group, but the ratios of both liver or spleen to body weight were increased in mice injected with 20mg/kg and 40mg/kg. These results suggest that the glycoprotein from Urechis unicinctus could stimulate immunity of the mouse bearing tumor cells. Furthermore, the number of leucocytes was also increased by 38.78% at the dose of 20mg/kg and by 46.30% of control at 40mg/kg, while the lower level of 2mg/kg or 4mg/kg showed no effect in increasing leucocyte number. The biochemical values such as GOT and GPT in serum were not changed in mice injected with glycoprotein in comparision with control group.