We employed southern analysis to examine homology between yeast genes RAD 51, RAD 52, RAD 54, and RAD 55 for possible gamma repair genes in radioresistant or repair proficient human tumor cell lines and normal placental DNA. No homology wa observed; however, other strategies including further gene restriction and transfection are underway to identify repair genes in human tumors. Understanding mechanisms of radiation repair might lead to more effective clinical radiation treatment protocols.