Oxidative stress has been implicated as a common pathogenetic mechanism in neurodegenerative disorders. Central nervous system is particularly exposed to free radical injury, given its high metal content, which can catalyze the formation of oxygen free radicals, and the relatively low content of antioxidant defenses. Indeed, several studies show markers of oxidative damage - lipid peroxidation, protein oxidation, DNA oxidation and glycoxidation markers - in brain areas affected by neurodegenerative disorders. Oxidative stress damage is intimately linked to glutamate neurotoxicity - known as "excitotoxicity". An excessive concentration of extracellular glutamate over-activates ionotropic glutamate receptors, resulting in intracellular calcium overload and a cascade of events leading to neural cell death. In this study we reviewed pathogenetic mechanisms that link oxidative stress and excitotoxicity in three neurodegenerative disorders (Alzheimer's disease, amyotrophic lateral sclerosis and Parkinson's disease) and described peripheral markers of these mechanisms, that may be analyzed in patients as possible diagnostic and therapeutic tools.