AIM: The aim of this study was to investigate the effect of oxidative stress on nucleosome levels and its relation with the clinical features in schizophrenia patients. MATERIAL AND METHOD: Thirty schizophrenia patients and 30 healthy controls were enrolled in this study. Patients were diagnosed with schizophrenia according to the 4th edition of the Diagnostic and Statistical Manual for Mental Disorders (DSM-IV). The control group consisted of 30 healthy subjects matched to the patients with regard to age and gender and who had no history of any psychiatric disorder. The severity of schizophrenia symptoms in the patients was evaluated using the Positive and Negative Syndrome Scale (PANSS) and the Clinical Global Impression Severity Scale (CGI-S). Physical and neurological examinations were performed in each of the patients and controls. RESULTS: Nucleosome, total oxidant levels and OSI values were higher in schizophrenia patients than in controls (p < 0.05). There was no signifi cant difference in the total antioxidant levels. There was a positive correlation between the nucleosome level and PANSS positive subscale (p = 0.028, r = 0.402). There was a positive correlation between TAS and age (p = 0.025, r = 0.289), PANSS total (p < 0.001, r = 0.604). There was a negative correlation between OSI and PANSS total (p = 0.019, r = -0.427), PANSS positive subscale (p = 0.043, r = -0.372). There was a negative correlation between TOS and PANS total (p = 0.028, r = -0.402). CONCLUSION: In this study we found a correlation between nucleosome level and PANSS positive subscale. To our knowledge, this is the fi rst study that evaluates oxidative stress and nucleosomes released from apoptotic cells together (Tab. 2, Ref. 50). Text in PDF www.elis.sk.