Abstract Superoxide dismutase (SOD), neuron specific enolase (NSE) and lactic dehydrogenase (LDH) were measured in the serum and cerebrospinal fluid (CSF) of ischemic cerebrovascular patients, other neurological patients and in age-matched healthy controls (serum only). The levels of SOD in the CSF or serum of the ischemic patients in the first 24 hrs after stroke were similar to the control groups. However, SOD levels in the ischemic patients increased after two days, reaching their peak values after one week (2–3 fold of the initial values). NSE showed a similar kinetics while LDH showed no change. These results suggest that oxygen radicals are formed in the ischemic patients and the increased synthesis of SOD may protect the patients from the potential damage of such radicals.