The present study analyses collagenous and non-collagenous components from age-matched normal and keratoconus corneas. Intact keratoconus corneas showed decreased collagen, total protein, and hydroxylysine levels, with normal reducible collagen cross-linking. Non-collagenous fractions were isolated from corneas with a 4 M guanidine procedure. As demonstrated by PAGE-silver stain, the keratoconus cornea guanidine extracts had a 75 kDa band that was absent in normal cornea guanidine extracts. In addition, there was a markedly increased level of protein, uronic acid and neutral hexose in keratoconus extracts as compared with controls. Our Western blot studies showed increased affinity for the castor-bean agglutinin (RCA120, specific for terminal galactose) in the keratoconus extracts as compared with normals. These data suggest the presence of an abnormal noncollagenous component in keratoconus corneas.