Background. Oxidative stress may play an important role in rheumatoid arthritis (RA) etiopathogenesis. The thiol group is a very strong antioxidant. In this study, we aimed to investigate the presence of oxidative stress in patients with RA by evaluating thiol/disulfide homeostasis. Material and methods. A total of 50 female RA patients and 50 healthy female controls were included in this study. Thiol and disulfide values were calculated utilizing novel methods.