chondroitin sulfates were isolated from the mud snail. For the quantitative analysis of enzymatic digestion products of isolated chondroitin sulfates, strong anion exchange-high performance liquid chromatography (SAX-HPLC) was performed. by the action of chondroitinase ABC, three unsaturated disaccharides$ 2-acetamide-2-deoxy-3-O-({eta}-D-gluco-4-enepyranosyluronic acid)-D-galactose $$({Delta}Di-OS), $2-acetamide-2-deoxy-3-O-({eta}-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D-galactose ({Delta}Di-6S) and 2-acetamide-2-deoxy-3-O-({eta}-D-gluco-4-enepyranosyluronic acid)-4-O-sulfo-D-galactose ({Delta}Di-4S)$ were produced from the mud snail chondroitin sulfates. The analysis showed that relative proportion of ${Delta}Di-OS/{Delta}Di-6S/{Delta}Di-4S$ was 58.7/3.1/38.2. The immunomodulating activity of chondroitin sulfate was examined by cell proliferation assay and these results suggest that it might be a immunosuppressant.