Protein-polysaccharide complexes were prepared in three different ways and the gross stoicheiometry of the complexes compared. 2. The neutral sugar content was ascertained and the possibility of a glycoprotein occurring with chondroitin sulphate and keratosulphate is discussed. 3. Physical data support a molecule of molecular weight 3.2x10(6)-5.8x10(6) with a roughly spherical domain and an average radius of gyration of 1390A. Such a particle is highly solvated. The complex is heavily charged with the sulphate groups on the outside. 4. These findings are discussed in the light of the physiological role of protein-polysaccharide light fraction (PPL) in cartilage.