Age- related neurodegenerative diseases, especially Alzheimer's disease (AD), are an important health problem globally. AD is clinically characterized by loss of memory, reasoning and speech. The frequency of the disease reaches to 20-40% in the population over the age of 85. Autopsy findings have indicated the presence of senile plaques and neurofibrillary tangles in the brains of patients with AD. These two lesions can be seen in small numbers during normal aging of the brain but occur in large amounts during AD. Although the initiating causes leading to AD are unknown, oxidative damage appears to play an important role in the slowly progressive neuronal death that is characteristic of AD. Indeed, in addition to the presence of senile plaques and neurofibrillary tangles, postmortem analysis of AD brain has also identified markers of oxidative stress including protein nitrotyrosine, carbonyls in proteins, lipid oxidation products and oxidized DNA bases. This review discusses the role of reactive oxygen and nitrogen species in the pathogenesis of AD and examines the relevance of antioxidant therapy in altering and/or inhibiting neurodegeneration associated with the disease.