Objectives: Thrombosis usually associated with many mutations, the condition which predisposed for recurrent pregnancy losses in women. In the present study we aimed to test the link between recurrent pregnancy losses and C677T missense mutation of 5, 10-methylenetetrahydrofolate reductase in Egyptian women. Methods: In the present study we tested the methylenetetrahydrofolate reductase (MTHFR) C677T gene mutation, MTHFR activities in placental tissues and serum homocysteine level in Egyptian women with a history of recurrent pregnancy losses .The study included 150 subjects of a history of more than one recurrent pregnancy loss matched with 100 normal subjects with a history of normal delivery with no complications. Results: MTHFR C677T mutation was detected in (45.4%) of patients and in (4%) of control. Homozygous with mutant alleles were detected only among patients. The lowest placental MTHFR activities were detected among patients with heterozygous mutations, a significant increase in the plasma homocysteine is observed in all patients with MTHFR mutation compared with control. Conclusion: MTHFR C677T mutation is significantly involved in RPLs in Egyptian women.