Parkinson's disease affects one out of every 100 people above the age of 55. Its cause is unknown and although the symptoms can be treated, there is no cure. The disease is associated with the selective loss of neurons that contain biogenic amines, and among these it is the dopamine (DA) neurons of the nigrostraital projection that are the most consistently and severely affected (Bernheimer et al., 1973). In this review we discuss the possibility that DA may act as an endogenous neurotoxin, causing the degeneration of the very neurons that release it. We further suggest that although treatments which increase the synthesis and release of DA reduce the symptoms, they also may serve to exacerbate the neurodegenerative process. We propose that the treatments which increase the antioxidant capacity of brain may be protective.