In recent years, intense efforts have been made to clarify the pathogenesis of urolithiasis, which affects more than 10% of the population of developed countries. Currently, a number of studies have assumed a key role in the pathogenesis of oxalate urolithiasis, which is the most common one that belongs to the active forms of oxygen generated in the kidney, as a result of the activation of free radical oxidation that occurs in the interaction of calcium oxalate crystals with renal tubular epithelial cells. In the current work, oxidant and antioxidant status were assessed in the blood of patients with complicated urolithiasis pre – and post surgery. The surgical treatment of complicated urolithiasis leads a decrease of the oxidative stress and an increase in the potential of antiradical and antiperoxidative protection.