Abstract
In this article, some of the history that has gotten us to this point will be reviewed, with a particular emphasis on the MPTP story. Where appropriate, future research directions will be sketched out. At the same time however, one of the broader purposes of this article is to perform what might be called a "reality check" on current research, by providing a gentle reminder of the many phenomena that must be explained by any etiologic hypothesis which is to be seriously considered.