Deinococcus radiodurans（Dr）, possesses a prominent ability to repair DNA injury induced by various DNA-damaging agents including mitomycin C （MC）,ultraviolet light （UV） and ionizing radiation. A DNA repair mutant Dr KH3111 is a streptomycin resistant （Sm,R,） derivative of KH311 which was generated by treatment with nitrosoguanidine and was sensitive to MC,UV and γ-ray irradiation. DNA damage resistance was restored in KH3111 by transforming with DNA of a cosmid clone pDC144 constructed from genomic DNA of Dr KD8301. The high transformation efficiency of KH3111 with DNAs of pDC144 derivatives indicates that the mutant is proficient in natural transformation competence,suggesting that recombinational repair is not defective in the mutant. Gene affected by a mutation in the mutant was identified and its nucleotide sequence was determined. A complete open reading frame （ORF） which encompassed the KH3111 mutation region was found and tentatively designated ,orf,144,b,. The deduced amino acid （aa） sequence of ,orf,144,b, consists of 284 aa and has no significant homology to other known proteins. The exact KH3111 mutation site was identified by sequencing DNA fragments amplified from genomic DNA of the mutant. One nucleotide was altered （G to A） in the sequence of ,orf,144,b, in the mutant. The KH3111 mutation causes the substitution of Gly for Glu at aa position 149 of Orf144b. It appears that the Gly substituted by this mutation would be one of the important residues to fulfill the function involved in DNA repair in Orf144b. Survival measurements of a revertant KH3112 which was generated by transforming with DNA of a polymerase chain reaction （PCR） product containing a part of the ,orf,144,b, gene of KD8301 showed that the resistances to MC,UV and γ-ray in the revertant were fully restored at equal level with wild type,indicating that the characteristic sensitive phenotype of KH3111 can be accounted for by the point mutation in the novel gene. Thus,the ,orf,144,b, gene required for the multiple-DNA-damaging agent resistance of Dr was designated pprA （pleiotropic gene promoting DNA repair）.