Polymorphisms of the x-ray repair cross-complementing group 1 (XRCC1) gene have been reported to be associated with various forms of cancer. We evaluated the possible effects of the Arg194Trp and the Arg399Gln polymorphisms on the risk for chronic lymphocytic leukemia (CLL) in 73 patients and 50 controls. We also analyzed their relation to frequency of sister chromatid exchange (SCE). With respect to codon 194, the allelic frequency of the Arg194Trp polymorphism did not significantly differ between the 2 groups. The proportion of individuals carrying the Arg194Trp polymorphism was not different in the 2 groups. With respect to codon 399, the proportion of the individuals carrying the Arg399Gln allele (90% vs 62%; p = 0.000; odds ratio [OR], 5.779; 95% confidence interval [CI], 2.2-15.183) and the allelic frequency of the Arg399Gln polymorphism (56% vs 36%; p = 0.002; OR, 2.278; 95% CI, 1.350-3.843) was significantly higher in the patient group. The frequency of the Arg/Gln genotype was significantly higher in the patient group (68.50% vs 52%; p = 0.049; OR, 2.007; 95% CI, 0.955-4.217). The mean SCE frequency in the patient group was significantly higher (9.2 +/- 4 vs 7.5 +/- 2; p = 0.02). When different compound genotypes were compared, the coexistence of Arg/Arg genotype in codon 194 with Arg/Arg genotype in codon 399 was significantly more frequent in the control group (30% vs 9%; p = 0.004; OR, 0.247; 95% CI, 0.092-0.664). Within the patient group, SCE frequency did not differ between patients with various genotypes. The Arg399Gln polymorphism may be etiologically associated with CLL; however, it does not seem to increase SCE frequency.