DNA polymerase iota (pol iota) is one of several recently discovered DNA polymerases in mammalian cells whose function is unknown. We report here that human pol iota has an intrinsic 5'-deoxyribose phosphate (dRP) Lyase activity. In reactions reconstituted with uracil-DNA glycosylase (UDC), apurinic/apyrimidinic (AP) endonuclease and DNA Ligase I, pol iota can use its dRP Lyase and polymerase activities to repair G . U and A . U pairs in DNA, These data and three distinct catalytic properties of pol iota implicate it in specialized forms of base excision repair (BER).