BACKGROUND The expression of the 5,10-methylentetrahydrofolate reductase (MTHFR) gene in human oocytes and preimplantation embryos suggests that the MTHFR gene is involved in folliculogenesis and female reproduction. Considering the importance of the MTHFR gene on female reproduction, the aim of this study was to evalu- ate the influence of MTHFR C677T polymorphism on ovarian marker reserve, particularly serum anti-Müllerian hormone (AMH) levels, and ovarian response as well as clinical pregnancy rates after in vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI). METHODS A total of 137 women who underwent ART treatment due to male factor infertility enrolled in this study. Genotyping of MTHFR C677T polymorphism and serum AMH concentrations were performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique and an ultrasensitive enzymelinked immunosorbent assay (ELISA). RESULTS Women with the TT genotype showed significantly higher AMH levels (4.5 ± 3.2 ng/mL) compared to carriers of other genotypes after ovarian stimulation. We observed a nonsignificant trend towards lower clinical pregnancy rates in patients with the TT (23.1%) versus CT (48.4%) genotypes (p = 0.2). No significant differences existed in terms of miscarriage and live birth rates among the groups. Multivariable logistic regression revealed that the duration of infertility and AFC were important predictive variables for the live birth rate. CONCLUSIONS Our results confirmed that the presence of the T mutant allele of the 677 polymorphism in the MTHFR gene led to an increased trend in AMH levels. Interestingly, we observed that the numbers of oocytes retrieved decreased in the mutated genotypes. We have not observed this trend in relation to oocyte maturity. The influence of the MTHFR C677T polymorphism on embryo quality and pregnancy rate after ART cycles remains unclear.