Objective: To analyze the methylenetetrahydrofolate reductase (MTHFR) mutation in recurrent spontaneous abortion associated with hyperhomocysteinemia. Material and Method: The blood sample of habitual aborter with high fasting homocysteine level was tested by PCR - RFLP method. Results: The patient was found to be a homozygosity for MTHFR gene mutation that was confirmed by the finding which is consistent with the mutation at the nucleotide 677 C to T, corresponding to Ala to Val. Conclusions: Hyperhomocysteinemia due to MTHFR mutation is a cause of recurrent spontaneous abortion. Therefore, the MTHFR mutation should be examined in the workup of recurrent spontaneous abortion showing hyperhomocysteinemia.