Encouraged by recent studies on the MTHFR 677C>T polymorphism and breast cancer risk that suggested an association of the 677 TT genotype with increased breast cancer susceptibility in premenopausal women, we performed an analysis of the relationship between breast cancer risk and the MTHFR 677C>T polymorphism in 210 premenopausal breast cancer patients and sex- and agematched healthy control subjects. Our data show a trend for a higher MTHFR 677T allele frequency in breast cancer cases (61.9%) than in controls (51.5%, P = 0.082) supporting the results of previous studies.