Twenty years ago this fall I was transformed suddenly, with little warning or preparation, from a zoologist interested in parasitic worms into a public health helminthologist. Since that time I have spent considerable effort in defining to a friendly, but at times rather skeptical, audience of students, colleagues, and co-workers, the place of helminthology in the rapidly developing field of public health. The opportunity given me this evening is a recognition of the importance in tropical medicine of the field I represent. Here is a chance, too good to miss, to ride my hobby and boost my subject before a dinstinguished group of scientists, in no position for the moment to put up any effective resistance. I have decided, therefore, to point out briefly some of the ways in which research on parasitic worms and control programs against helminth diseases have played a part in public health progress.