Systemic sclerosis (SSc) is a disease characterized by fibrosis of the skin and organs; it is associated with diffuse fibroproliferative microangiopathy and autoimmune background. The studies have shown that the production of excessive free radicals and increased collagen synthesis by the fibroblasts play an important role in the pathophysiology of SSc. Prolidase is an important marker in collagen turnover. We aimed to compare total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), and prolidase levels of SSc patients and healthy controls. We also investigated the relationship between prolidase and oxidative stress.