The human multidrug resistance (MDR-1) gene encodes P-glycoprotein (Pgp), which affects the pharmacokinetics of many drugs. Here, we investigated whether common MDR1 single nucleotide polymorphisms (SNPs) (C3435T and G2677T) affect predisposition to B-chronic lymphocytic leukemia (B-CLL). Genotyping was performed in 65 patients with CLL and 70 controls using polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP). We observed a higher frequency of carriers of 3435CT gene among B-CLL patients as compared to normal individuals (58.5% vs. 22.9%, p=<0.001). The genotypes 3435CT was associated with B-CLL, [odds ratio=4.8, 95% confidence interval=2.3-10.0]. Moreover, patient and control groups did not differ significantly regarding MDR1 genotype (G2677T). Furthermore, no correlation was shown between the MDR1 (3435 or 2677) genotypes and clinical and laboratory data of patient group. In conclusion, these data indicate that the MDR1 C3435T SNP may carry an increased risk of developing B-CLL.