It was found that all schizophrenic patients who did not have antibodies against Toxoplasma gondii had the wild type CC genotype (p = 0.003), while patients diagnosed with schizophrenia and with the positive result for the antibodies against Toxoplasma gondii, possessed the allele T of MMP-9-1562C/T polymorphism. The gene discussed is MMP9; the disease is schizophrenia.