Epidemiological studies have suggested that hormones, genetic factors, and environmental agents are significant risk factors in breast carcinogenesis. Some pesticides have the ability to act as xenoestrogens in vivo. The CYP19 gene encodes the aromatase enzyme which is involved in the estrogens biosynthetic pathways. We have assessed the frequency alleles of a (TTTA)(n) repeat of CYP19 gene in breast cancer patients which were either exposed or not exposed to specific pesticides. No differences were observed in the distribution of the alleles between the two groups showing that the polymorphism does not have a significant functional role on the aromatase activity. When compared to healthy control Greek women group, only the (TTTA)(10) repeat variant presented a non-significant increased risk in breast cancer susceptibility [odds ratio (OR): 2.46, P>0.05 ]. Lack of strong association suggests that the polymorphic TTTA short tandem repeat of CYP19 gene may have not a functional effect on the enzyme's activity and thus its role in the development of breast cancer remains unclear.