Experimental studies have demonstrated that oxidative stress plays an essential role in the pathophysiology of ischemic stroke. The objective of the present study was to assess some serum markers of oxidative stress in patients in the early period of ischemic stroke and determine whether vitamin C supplementation affects the parameters of oxidative stress and the clinical status of patients. The study included 60 patients with ischemic stroke and 20 controls. Patients with ischemic stroke were divided into two groups: group I (n = 30), which did not receive vitamin C therapy, and group II (n = 30), which received vitamin C (500 mg/day, i.v.) for 10 days beginning on day 1 after ischemic stroke. Blood levels of bilirubin, creatinine, uric acid and total antioxidative capacity (TAC) were measured on stroke-days 1, 3, 5, and 10. Moreover, the neurological status of patients was evaluated on the same days using the NIHSS, Rankin and Bartel scales. Neurological status was also assessed with the Rankin scale after 3 months. Uric acid and TAC were decreased in group I on all measurement days. However, we did not observe any differences in the clinical status of patients receiving vitamin C during the first ten days of stroke or after 3 months. Although administration of vitamin C (500 mg/day, iv) to ischemic stroke patients since the first day ischemic stroke resulted in elevated serum levels of antioxidants, it did not substantially improve the clinical and functional status of patients after 3 months.