Proteohyaluronic acid was extracted from human umbilical cord with 0.2% NaCl, then purified by cetylpyridinium chloride (CPC)-precipitation, DEAE-cellulose column chromatography, gel-filtration on Sephadex G-200 and on Sepharose 4B, in succession. The purified preparation contained glucosamine (40.1%), glucuronic acid (45.7%) and protein (2.6%). Glutamic acid, glycine, alanine, serine and aspartic acid were the major amino acids of the protein moiety. The result of the gel-filtration suggested that an average molecular weight was more than 1×10⁶. Although analytical data for the constituent sugars and infrared spectra were similar before and after pronase digestion of this proteohyaluronic acid, the mobilities in electrophoresis and the elution patterns of gel-filtration differed remarkably from one another. Since the protein content decreased from 2.6% to 0.3% by the proteolytic digestion, it is evident that the degraded protein moiety played an important role in maintaining the macromolecular structure of this proteohyaluronic acid.