Murine corneal aldehyde dehydrogenase has been purified to homogeneity and characterized with a range of aldehyde substrates at pH 7.4. The enzyme was a dimer with a subunit molecular weight of 59 KDa. and appears to prefer aldehyde products of lipid peroxidation as substrates. The enzyme constituted approximately 5% of the total soluble protein of mouse cornea. A dual role has been proposed for corneal aldehyde dehydrogenase in providing the eye with protection against UV-B light: by oxidizing aldehydes generated through light-induced lipid peroxidation; and by the direct absorption of UV-B light by the enzyme.