The estrogen receptor (ER) and the human epithelial growth factor receptor 2 (HER2) genes have been implicated in the development and prognosis of breast cancer. Several genetic polymorphic sites in these genes have been identified and associated with the risk of breast cancer. We have investigated the association between the estrogen receptor codon 594 (ACA to ACG) and HER2 codon 655 (ATC to GTC) polymorphisms and breast cancer risk. Genomic DNA from breast cancer patients and control subjects was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). When allelic frequencies of the ER codon 594 and HER2 codon 655 gene were compared, no significant differences were observed between the patient and control groups. (P = 0.063, OR = 1.55, 95% CI = 0.25-9.41 and P = 0.949, OR = 1.01, 95% CI = 0.55-1.88, respectively). In conclusion, our results support the view that both the ER codon 594 and HER2 codon 655 polymorphisms are not associated with increased risk of breast cancer.