Selenium's most well-established role is as a component within the active site of the antioxidant enzyme, glutathione peroxidase. Glutathione peroxidase helps prevent the generation of free radicals and decreases the risk of oxidative damage to tissues, including the kidney and its vascular components. Low-selenium intake and status is of concern during chronic renal failure, when dietary protein restrictions are necessary, because dietary selenium is primarily associated with protein. Depressed selenium status occurs frequently in renal patients and should be of concern because of the possible exacerbation of comorbid conditions. Oral and intravenous selenium supplementation has proven to be effective in improving the selenium status and immune function of renal patients, while at the same time decreasing the products of oxidative stress. Therefore, it seems beneficial to monitor selenium status in patients with chronic renal disease and correct less-than-optimal status with careful selenium supplementation.