It is now well recognized that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) can induce a syndrome in human and non-human primates similar to Parkinson's disease. This highly selective neurotoxin, which affects specific catecholaminergic nuclei in the brainstem, has provided an important new tool for the study of Parkinson's disease. In this article we review several specific areas related to current research on MPTP, including the question of disease progression, issues regarding the validity of the animal model induced by MPTP, the role of aging in regard to its neurotoxicity and Parkinson's disease, and new therapeutic strategies that have evolved from basic research with the compound. We conclude that both clinical and basic research stemming from the discovery of MPTP have provided valuable insights regarding both the cause and treatment of Parkinson's disease.