Since excess Hcy and the presence of MTHFR SNPs increase pathology risks in general [9–12], the risk of infertility at all stages pre- and post-conception [13–18], the frequency of miscarriage [6, 19, 20], and compromised infant health [21–23], we have determined retrospectively the prevalence of the two main MTHFR SNPs in our population of 2970 male and female patients consulting for infertility; serum homocysteine levels were assessed in parallel. The gene discussed is MTHFR; the disease is Infertility.