Abstract: Objective To investigate the relationship between polymorphisms of CYP1A1 and CYP 1B1genes and the susceptibility to recurrent pregnancy loss(RPL).Methods The MspI polymorphism of CYP1A1 and the polymorphism in exon 3 codon 432(C-G of CYP1B1)were detected with the methods of polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP)and allele specific-PCR(AS-PCR)in a case-control study including 81 cases of RPL and 98 healthy controls.Results There was no significant correlation between MspI polymorphism and RPL susceptibility(χ²=0.335,P=0.846).There were significant differences in the genotype distributions or allele frequencies of CYP1B1 L432V polymorphism between the two groups(χ²=7.467,P=0.024;χ²=9.129,P=0.003). Compared with wild-type C/C,the susceptibility of recurrent abortion with the genotypes of homozygotic mutation G/G and heterozygotic mutation C/G were increased by 2.620 and 1.954 times,respectively.Compared with allele C,the risk of recurrent abortion with allele G was increased by 2.038.Conclusion The gene polymorphism of CYP1B1 in exon 3 condon 432(C-G)might be a genetic risk factor of RPL and the allelic polymorphism of CYP1B1 L432V increases the risk of recurrent abortion.The results do not show that polymorphism of MspI is associated with the susceptibility of RPL.