From March 1, 2005 to December 31, 2008, the polymerase chain reaction-restriction fragment length polymorphism method was applied to evaluate genetic polymorphisms of the XRCC1 codon399 (Arg/Gln) and XPD codon751 (Lys/Gln) DNA repair genes in 108 patients with stage IIIB and IV NSCLCs treated with platinum-based chemotherapy in the Department of Chemotherapy of Jiangsu Cancer Hospital and Research Institute.