The anititumor and immunologic activities of the glycoproteins extracted from sea cucumber (Stichopus japonicus) on mice bearing sarcoma 180 cells were investigated . Maximum tumor suppression (64%) occurred at the dose of 100mg glycoprotein/kg. The highest prolongation ratio was achieved at the level of 100mg/kg an dincreased by 395 more than that of control. Glycoproteins from sea cucumber exhibited direct cytotoxic effect on the tumor cells. Dose dependent increase of leucocyte, peritoneal exudate cell and weights of immunoorgans revealed the improvement of immunity. When the glycoportein-administered group was compared with the control, a significant difference was not noted in the clinico-chemical values such as S-GOT, S-GPT , alkaline phoshatse activity, total protein, cholesterol, triglyceride, urea nitrogen and glucose levels in blood. These results suggests that the antitumor activity of sea cucumber glycoprotein is associated with activation of cells in the immune system.