Background: Thiol-disulphide homeostasis has vital role in cell signalling mechanisms, regulation of transcription factors and enzymatic activities, signal transduction and regulation of proliferation rate, apoptosis and detoxification and antioxidant protective mechanism. Objective: This study aims to demonstrate in Polycythemia Vera (PV) patients the thioldisulphide homeostasis which is known to play a role in cell proliferation, apoptosis and various steps of cell cycle. Design: Descriptive prospective cross-sectional study. Settings: Yildirim Beyazit University Hospital Ankara, Turkey between 2016-2018. Method: Forty-two PV patients and 43 healthy controls were included in the study. Serum total (–SH + –S–S–) and native (–SH) thiol levels were measured in all subjects. The amount of dynamic disulphide bonds and, the ratio of (–S–S–) and (–S–S–) × 100/(–SH), (–S–S–) × 100/(–SH + –S–S–), and –SH ×100/(–SH + –S–S–) were calculated with automatic method. The data obtained from the patient group were compared with the control group. Main outcome measures: The amount of dynamic disulphide bonds and, the ratio of (–S–S–) and (–S–S–) × 100/(–SH), (–S–S–) × 100/(–SH + –S–S–), and –SH ×100/(–SH + –S–S–) were calculated with automatic method in PV patieint and healthy control group. Results: Both groups were similar in terms of age and gender distribution. Compared with the control group, PV group had significantly higher native thiol, total thiol and nativ/total thiol levels. Limitation: The generalizability of the study's findings were limited by the small sample size. Conclusions: In accordance with the nature of the disease, thiol balance in PV patients was in favor of proliferation. Increased total thiol (–SH + –S–S), native thiol (–SH) levels and native thiol/total thiol ratio might be associated with uncontrolled proliferation. The balance of the thiol-disulphide homeostasis shifted to reductive thiol side in the PV. This change can provocate proliferation status of the disease and/or may be secondary to the disease. Conflict of Interest: No conflict of interest was declared by the authors.