Amplification and/or overexpression of HER-2/neu has been reported to be associated with poor prognosis in breast cancer. One single-nucleotide polymorphism at codon 655 indicates a guanine-to-adenine substitution (Ile655Val) in the transmembrane domain-coding region of the HER-2/neu gene reported to be associated with increased risk of breast cancer. However, several studies have shown that this association is controversial. In this study, we aimed to evaluate the association between HER-2 codon 655 polymorphisms and breast cancer risk in breast cancer patients. We analyzed the HER-2 codon 655 polymorphisms in paraffin block sections from 58 breast cancer patients and 55 control subjects and evaluated the association of the polymorphic alleles with breast cancer. Following DNA isolation, polymerase chain reaction-restriction fragment length polymorphism analysis was carried out. The polymorphic Val allele was detected in 12.1% of the patients and in 17.3% of the control subjects. When the results of the study were evaluated, no statistically significant correlation was found between HER-2/neu codon 655 polymorphism and breast cancer.