This bulletin is about an invasion that was welcomed. It tells how boys and girls of Petersburg, West Virginia, invaded their town to learn and to serve. Hotels, school lunchroom, alleys, creeks and swamps, unused park area, and other resources were utilized. The young invaders were welcomed by the adult citizens of the town because the principal of the school had sent those who might be interested a letter asking them to receive the boys and girls and help them with a school health project. "How healthful is Petersburg?"--that's what the children wanted to know; and "How can we help to make it more healthful?" This bulletin tells how the boys and girls organized their campaign to get information. It explains why information was not enough, and how the campaign to get information was followed by cooperative plans for improvements when these were needed. The work described here was done by children, school staff, and patrons cooperatively. The Petersburg community was enabled to develop this health program partly through a grant from the W. K. Kellogg Foundation of Michigan to the West Virginia State Department of Education. The object of the grant was to establish 3-year demonstration centers in certain schools of the State, one of which was the Petersburg Elementary School, for experimenting with ways of improving school and community health. Among the goals of the demonstration center program were the following: (1) to discover means of making health education as functional as possible; and (2) to learn ways of using the community as a laboratory and a field of civic service in health improvement. It is the purpose of this bulletin to show how the Petersburg Elementary School and community achieved these goals and thus took several steps toward a way of life not only for today's citizens, but for tomorrow and the day after, and the day after that. (Contains 4 footnotes.) [Best copy available has been provided.]