Since a folate pool imbalance and impaired repair mechanisms may result in DNA instability and strand breaks, and inactive MTHFR C677T may accelerate the carcinogenesis process of DNA hypomethylation under folate deficiency conditions, we hypothesized that folate deficiency and inactive MTHFR C677T may influence both susceptibility to and progression of ovarian cancer. This evidence concerns the gene MTHFR and folate deficiency.