Many scientists agree that the genes involved in the aetiology and pathogenesis of psychiatric diseases could serve as biomarkers – biological indicators of the health status. Genetic markers may inform about general predispositions of a person to develop certain diseases, while other biochemical factors, such as concentrations of substances in body fluids, reflect the actual condition of the organism. Researchers involved in studies on schizophrenia are interested in the gene and protein of the brain-derived neurotrophic factor (BDNF) due to the role of this neurotrophin in the process of neurogenesis, synaptogenesis and its influence on the functioning of dopaminergic neurons. Among patients diagnosed with schizophrenia, the BDNF gene polymorphisms and methylation in the promoter sequences were studied. The neurotrophin was also assayed in the blood of patients, also taking into account the effect of pharmacotherapy on the BDNF concentration, and post-mortem in the brains of the patients. The results of current studies are contradictory. The only systematically confirmed observation is the lowered concentration of BDNF in the serum of patients with schizophrenia compared to healthy controls. It seems that so far our knowledge about the BDNF gene expression and the functions of the protein is not sufficient to include BDNF analysis in the clinical assessment of patients with schizophrenia.