As one surveys the Public Health field it seems odd that there is not a generally accepted definition of its aims. That may not be an indictment, as this is a relatively young public service, and like a very active ameba, it is placing out many pseudopods in discovering its relationships. As a part of the program in fostering good health, with emphasis on both physical and mental health, an individual concerning himself with such service must include, then, mental hygiene. we must have some concept of its background, some realization of its need, and some conviction of the value of the psychiatric casework approach to people.