Understanding of opinion leadership is provided by a classic study of the spread of an important educational innovation, modern math, among the thirty-eight school superintendents in Allegheny County, Pennsylvania, which is essentially the city of Pittsburgh. The innovation of modern math began in the early 1950s, when top mathematicians in the United States completely overhauled the mathematics curriculum of public schools. Out of their efforts came “modern math”, a radically new approach to teaching mathematics that was packaged to include textbooks, audiovisual aides designed for teaching the new concepts, and summer institutes to retrain school teachers in the new subject matter. The innovation spread relatively quickly because of powerful federal sponsorship by the National Science Foundation and the U.S. Department of Education. Modern math was widely hailed by educators as a major improvement. It was quite different from the “old” math in that it used set theory, Venn diagrams, and an emphasis upon probability. Math teachers had to learn an entirely new approach to their subject.