Abstract: Anti-arthritic protide isolated from the bone of porcine limbs showed a single spot on thin layer chromatography and a single band by cellulose acetate electrophoresis. It presented both a strong band and a weak band by polyacrylamide gel electrofocusing. Its molecular weight determined by Sephadex G-100 is about 27,000. It contains no sugar. The protide was found to inhibit the swelling of the rat paw induced by egg albumin injection. We hold that the protide is an active principle for anti-arthritis activity in extracts of the porcine limbs bone.