The 677 C/T mutation of the methylenetetrahydrofolate reductase (MTHFR) gene was associated with schizophrenia in many studies. Objective: To analyze the presence of the mutation in patients with schizophrenia and its influence on clinical feature and the responsiveness to treatment. Material and method: 42 inpatients were psychiatrically and scalar evaluated. We performed DNA analysis of the 677C/T polymorphism of the MTHR gene. Results: The mutation was present in 28 (66.67%) of the patients compared to 12 (34.29%) of the control group (p=0.005). Patients with modified genotype had slightly higher mean scores in positive, negative and general symptoms. Patients with the mutation had a significant better response to atypical antipsychotics than patients with normal genotype (p<0.002). Conclusions: Our study confirms the role of the MTHFR 677C/T polymorphism in the etiopageny of schizophrenia. The presence of T allele was associated to atypical antipsychotics response, but not to the intensity of symptoms.