Proteoglycans of bovine compact bone were purified by chromatography of the formic acid precipitate of an EDTA extract. The sequential chromatographic steps consisted of gel filtration on Sepharose CL-6B in 4-M guanidine HC1, ion-exchange chromatography on DEAE-Sephacel in 4-M urea and rechromatography on Sepharose CL-6B in 4-M guanidine HC1. The preparation consisted of a relatively small proteoglycan (Kav = 0.4 on Sepharose CL-6B) containing about 40% protein, 21% hexuronic acid, 23% galactosamine and lesser amounts of other monosaccharides. The core protein was shown by gradient NaDodS04 gel electrophoresis, electrotransfer and immunodetection to be monodispersed with an Mr = 45,000. Analysis of glyco-peptides obtained after papain digestion of the proteoglycan and separation from glycosaminoglycan chains by gel chromatography, indicated that both AMinked and 0-linked oligosaccharides were present. The glycosaminoglycan chains liberated by papain digestion eluted from Sepharose CL-6B as a broad peak with Kav = 0.50, slightly ahead of the position of elution of bovine nasal cartilage glycosaminoglycans (Kav = 0.52); the bone glycosaminoglycans are thus slightly larger than those from cartilage and smaller than the ones attached to fetal bone proteoglycans. These chains were totally susceptible to chondroitinase AC II, a procedure that yielded unsaturated disaccharides corresponding predominantly to chondroitin-4-sulfate, and to a lesser extent chondroitin-6-sulfate. © 1985 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.