Objective: To analyze the methylenetetrahydrofolate reductase (MTHFR) mutation in patients with recurrent spontaneous abortion. Material and Method: The blood samples of patients with recurrent spontaneous abortion were tested by PCR-RFLP method. Results: Of 51 cases of study group, 14 (27.5%) were normal, 25 (49.0%) were heterozygosity, and 12 (23.5%) were homozygosity. Of 58 cases of control group, 20 (34.5%) were normal, 30 (51.7%) were heterozygosity, and 8 (13.8%) were homozygosity. But the difference between two groups was not significant (p=0.190). Conclusion: Hyperhomocysteinemia due to MTHFR mutation is a cause of recurrent spontaneous abortion. Therefore, the study for MTHFR mutation should be included in the workup of recurrent spontaneous abortion.