PIP: Diffusion is the process by which an innovation is communicated through certain channels over time among members of a social system. The diffusion of innovations is a communication theory which has laid the groundwork for behavior change models across the social sciences, representing a widely applicable perspective. The diffusion of innovations paradigm began with the 1943 publication of the results of an hybrid seed corn study conducted by Bryce Ryan and Neal C. Gross, rural sociologists at Iowa State University. The diffusion paradigm spread among midwestern rural sociological researchers in the 1950s and 1960s, and then to a larger, interdisciplinary field of diffusion scholars. By the late 1960s, rural sociologists lost interest in diffusion studies, not because it was ineffective scientifically, but because of lack of support for such study as a consequence of farm overproduction and because most of the interesting research questions were thought to be answered. Since 1943, more than 4000 research publications have appeared and diffusion research became a widely practiced variety of scholarly study in sociology and other social sciences. This paper describes some of the history of rural sociological research on the diffusion of agricultural innovations with the goal of understanding how the research tradition emerged and to determine how it influenced the larger body of diffusion research conducted later by scholars in other disciplinary specialties. The authors describe how diffusion of innovations research followed and deviated from the Kuhnian concept of paradigm development.