Introduction: This study aims to investigate the dynamic thiol/disulphincide homeostasis in patients with schizophrenia who have positive psychotic indications.Materials and methods: Forty-four patients (26 males, 18 females; mean age=34.408.98years) accepted at the Department of Psychiatry of the Ankara Numune Training and Research Hospital and 33 healthy controls (15 males, 18 females; mean age of 30.308.48years) were included in the study. Serum native thiol and total thiol were measured with a novel colorimetric, automated method. The disulfide levels and disulfide/native thiol ratios were also calculated from these measured parameters.Results: Serum native thiol and the total thiol concentration were significantly lower in schizophrenia compared with the control group (p<.05). Disulphide levels and disulfide/native thiol ratios were significantly higher in schizophrenia compared with the control group (p<.05). When the patients were divided into two groups according to those who used medication and those who did not for the last two months, it was found to be significantly higher in those who used disulfide and disulfide/native thiol medication than those who did not use medication.Conclusion: The disulfide/native thiol ratio in patients with schizophrenia who have been using medication for the last 2months has been found to be significantly higher than controls who have not been using medication, may be indicating that the level of native thiol does not increase in a correlation as high as the increase in disulfide levels. It demonstrates that thiol/disulfide equilibrium has shifted towards the disulfide. The excess disulfide amounts might associated with both disease itself and the using medication.