['Although vitamin D deficiency can change liver injury progression in patients with hepatitis C virus (HCV), the main molecular mechanisms involved are largely unknown. The first aim of this study was to evaluate the association between oxidative stress and hypovitaminosis D in patients with HCV. The second aim was to verify whether oxidative stress is involved in the molecular mechanisms related to liver injury.', 'The study included 147 participants: 89 controls and 58 patients with HCV (vitamin D < 30, n = 32; vitamin D > 30, n = 26).', 'Patients with HCV and hypovitaminosis D presented significantly higher aminotransferase-to-platelet ratio index (APRI; P = 0.0464) and viral load (P = 0.0426) levels than patients with HCV without hypovitaminosis D. Regarding oxidative stress, HCV patients with hypovitaminosis D had higher advanced oxidation protein products (P = 0.0409), nitric oxide metabolites (P = 0.0206) levels, and oxidative stress index (P = 0.0196), whereas total radical-trapping antioxidant parameter (P = 0.0446) levels were significantly lower than HCV patients without hypovitaminosis D. Vitamin D in patients with HCV showed inverse correlations with levels of iron (r = -0.407, P = 0.0285), ferritin (r = -0.383, P = 0.0444), APRI (r = -0.453, P = 0.0154) and plasma lipid hydroperoxides levels (r = -0.426, P = 0.0189).'] Is profile of oxidative stress markers dependent on vitamin D levels in patients with chronic hepatitis C?