Antitumor activity was tested by administration of reaction mixture of green onion extract and chitin to mice bearing sarcoma-180 cells. An intraperitoneal injection of mixture(20 mg/kg/day) to mice Have an 52% inhibition of tumor growth. Inhibition of tumor growth was found to be dose-dependent. When eighty miligrams of the mixture were administered, the weight of tumor was reduced significantly. HPLC analysis indicated the mixture was composed of N-acetyl-D-glucosamine, N-acetylchitobiose and N-acetylchitotriose.