In the last few years, an increasing amount of studies have been dedicated to the etiopathogenesis of age-related neurodegenerative disorders, such as Parkinson's disease, amyotrophic lateral sclerosis and Alzheimer's disease. The discovery of synthetic, as well as natural molecules, able to reproduce in the animals biochemical and morphological alterations of neurodegenerative disorders, has provided a major impetus to the "environmental" hypothesis of neurodegeneration. In this review, following a brief description of the ability of the nervous system to counteract the degenerative process, the main neurotoxic-based animal models for neurodegeneration are examined. These might give us interesting clues for understanding the pathogenetic mechanism(s) of neurodegenerative process.