Post-mortem human vitreous samples (liquid and gel) of comparable intrinsic viscosity values (n=3000 cc/g) were chromatographed on DEAE-Sephacel columns at 4°C using a linear salt gradient ranging from 0±0.4M NaCl. All samples examined produced numerous discrete hyaluronic acid (HA) fractions. The HA fractions from liguid vitreous were eluted at lower salt concentrations than those from gel vitreous. Several HA fractions from vitreous analyzed by circular dichroism (CD) displayed CD minima at 210 nm, with an ellipticity value of 14 to 16×103deg cm2d mole-1. However, all HA fractions from liguid vitreous showed lower ellipticity values and a weak positive signal above 240 nm. This signal was absent in HA fractions from gel vitreous. Results suggest that subtle but definite conformational differences involving carboxylic groups exist between gel and liguid vitreous hyaluronate.