The XP-E DNA repair correcting factor (XP-E factor) has been extensively purified from HeLa cell soluble extracts by ammonium sulfate fractionation at 25-50%, and eluted from phosphocellulose column with 215mM potassium phosphate (pH 7.5), DEAE cellulose with 80mM phosphate, and Heparin agarose with 300mM phosphate. These chromatographic patterns are distinct from those of XP-A, C, D correcting factors, respectively. Moreover, the Xp-E factor does not correct the defect in other complementation groups of XP-A, C, and D. These imply that each of the four correcting factors is physically unique and presumably involved in a unique excision repair function in mammalian DNA repair system. The extensively purified XP-E repair correcting factor does not have UV, AP endonuclease and α,β,γ polymerase activities, but shows DNA binding activity. This result concludes that the XP-E correcting factor might be DNA binding protein of which function is not clear yet.