Studies on the association between the Ile to Val polymorphism at codon 655 of the human epithelial growth factor receptor 2 (HER-2) gene and susceptibility to breast cancer have been reported for almost all ethnic populations, with both positive or negative conclusions. No study, however, has yet been focused on the possible association between this gene and its predisposition to benign breast lesions, especially on risk for fibroadenoma. We aimed to study the association of the single nucleotide polymorphism V655 HER-2 gene polymorphism with histologically verified breast fibroadenoma risk. We conducted a molecular epidemiological case-control study of 70 breast fibroadenoma cases without cellular atypia and 172 healthy female controls. We found that the Val variant allele and genotype frequency of this polymorphism is higher in cases with fibroadenoma; however, this difference was not significant (allele Val 655: 27.86 and 22.67% in fibroadenoma and controls, respectively; genotype Ile/Val: 35.71 and 38.37% and Val/Val: 10.0 and 3.49% in fibroadenoma and controls, respectively). Applying logistic regression analysis, we found an increased risk of fibroadenoma formation in carriers of the Val allele (odds ratio = 1.17; 95% confidence interval = 0.67-2.05), in which the highest risk was associated with homozygous genotype (odds ratio = 3.07; 95% confidence interval = 0.97-9.72), but this risk was not significant. Stratification by age (cut-off 45 years) revealed the highest risk of fibroadenoma among young women homozygous for the Val allele (odds ratio = 3.30). The risk, however, was slightly increased (odds ratio = 1.24) among older carriers of the aberrant allele in their genotype as well, but it was not significant. In spite of insignificant differences, our results indicate that HER-2 Ile655Val polymorphism, especially in a homozygous form might play some role in the etiology of breast fibroadenoma formation. The significance of this susceptibility, however, will have to be verified by larger studies.