Original PaperBreast cancer is developed from the breast tumors.There are more than 18 sub-types of this cancer. This type of cancer is the second cause of mortality in women (1,2). The etiology of breast cancer is multi factorial. Genetic factors are interfered in the etiology of breast cancer. The FAS gene, has a critical role in the tumor growth and metastasis (2). Two polymorphisms have been identified in the FAS promoter region one in the silencer region, G to A substitution at nucleotide position −670 (rs1800682) (3).Breast cancer is the second cause of mortality in women. The etiology of breast cancer is multi factorial. Genetic factors play an important role in the etimology of breast cancer. The FAS gene, has a critical role in the tumor growth and metastasis. Gene polymorphisms including -1377 G>A and -670 A/G in FAS gene have shown to change the transcription activities of this gene. The FAS genotypes were determined by polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP) in 115 breast cancer patients, 115 healthy controls, all female and selected from city of Mashhad in north-eastern part of Iran. BstuI and ScrfI were used as endonuclease enzymes to detect -1377G/A and -670A/G gene polymorphisms, respectively. GG, GA and AA genotype frequencies for FAS -1377 polymorphism in patients were 30.4%, 49.6% and 20%, whereas in healthy controls were 26.1%, 50.4% and 23.5%, respectively and there was no significant difference between case and controls (p=0.7).Additionally, genotype frequencies of FAS -670 AA, AG and GG in patient groups were 52.2%, 39.1% and 8.7% respectively . The result of genotype frequency in controls for FAS -670 AA, AG and GG was 47%, 41% and 10.4%, which Showed insignificant difference as compared with patients genotypes (p=0.78). These results showed that FAS−1377G/A and FAS -670 A/G gene polymorphisms had a strong linkage disequilibrium with p value <0.001. These results indicated the lack of association between FAS−1377G>A and FAS -670 A/G gene polymorphisms and risk of breast cancer. Moreover, a significant linkage disequilibrium was found betweenFAS−1377G/A and FAS -670 A/G gene polymorphisms in case and control groups.