Object: The aim of this study was to assess the effect of parental 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (677C/T and 1298A/C) on response to single-dose methotrexate (MTX) treatment in tubal ectopic pregnancy (TEP).Materials and methods: In this prospective cohort study, cases with unruptured TEPs were grouped into two according to their response to single-dose MTX treatment (Group 1: responsive, n:88; Group 2: unresponsive, n:21). The groups were compared with regard to baseline demographic and clinical parameters. As a main outcome measure, the independent effects of parental MTHFR gene polymorphisms on response to single dose MTX treatment were evaluated.Results: One hundred and nine unruptured TEP were included in the final analysis. The mean maternal age was 29.305.21 years, gravity 2 (min-max: 1-5), parity 1 (min-max: 0-4). The median serum beta-human chorionic gonadotropin (-hCG) was 1403.35MI/I (Q(1)-Q(3): 517-2564). The overall response rate was 81% (88/109). The groups were similar with respect to basic baseline demographic data and serum -hCG level. Binary logistic regression analysis showed that the presence of parental MTHFR677C/T and 1298A/C polymorphism were not independent factor predicting treatment success (p>0.05). The only independent factor for resistance to single dose MTX was the previous TEP (OR: 4.47 (1.18-16.9)).Conclusion: Parental MTHFR 677C/T and 1298A/C mutations do not predict the outcome of single dose intramuscular MTX treatment in unruptured TEP.