The variation and changes of glycosaminoglycans in human vitreous body from patients with retinal detachment were studied. The isolated glycosaminoglycans from normal vitreous were identified as hyaluronate, which is the main component (92%) and chondroitin sulphate (8%). In contrast, in pathologic samples up to 18% of total glycosaminoglycans were identified as chondroitin.sulphate. In addition, in pathologic vitreous two fractions of glycosaminoglycans about 10% were identified as undersulphated chondroitin and heparan sulphate. The hydrodynamic size of hyaluronate differs between normal and pathologic samples. In samples from the patients with detached retinas the hyaluronic acid was of small hydrodynamic size.