Oxidative stress resulting front increased free radical production and/or defects in antioxidant defences may be the cause of various neurodegenerative disorders. In this study, the roles of oxygen free radicals, nitric oxide, Superoxide dismutase, vitamin E and vitamin C were investigated in pure and complicated hereditary spastic paraparesis (HSP) patients. The results showed that plasma SOD, vitamin E and nitric oxide levels were significantly low in HSP patients. These findings indicate the influence of oxidative damage in the degenerative process of HSP. (C) 2008 Elsevier B.V. All rights reserved.