This study is concerned with the establishment of diffusion agencies, entities that supply or make an innovation available to the population at large. Although there have been other studies that focus upon this and related aspects of innovation diffusion [2; 3; 4; 5; 6; 7; 10; 15; 20; 28], the bulk of research in geography and other social sciences is oriented towards demand aspects of adoption, overlapping the broad topic of consumer behavior [17, 26]. Two types of diffusion agency location processes have been noted [5]. In the mononuclear case, a single propagator or economic entity establishes a number * This paper is part of ongoing research on the diffusion of innovation supported by the National Science Foundation (Grant G-36829). This support is appreciated. We also wish to thank the following: K. Jezierski for typing the manuscript, R. Selling for figures and maps, and J. Foley for a number of useful comments on an early version of this manuscript. 1 It is assumed that these agencies usually are interrelated in at least some (and often many) functional aspects. To the degree that such interrelationship occurs, the diffusion agencies may be seen to comprise a network or system. of diffusion agencies.' The locations of these and the temporal order in which the locations are filled appear to be the result of evaluating and ranking alternatives, primarily employing economic criteria such as profitability. Thus, the process may be seen in terms of a multiple facility location problem. In the polynuclear case each diffusion agency is established by a different entrepreneurial or economic entity (generally in a location corresponding to its own). Here, economic factors appear to operate only in terms of threshold conditions that make agency establishment economically feasible. An equally important aspect of the process is the exposure of the entrepreneur to the innovation, whereby he learns of the method by which a diffusion agency is established and of the possibility and profitability of doing so. Thus, the polynuclear case may be seen as involving the spread of diffusion agencies with adoption of an entrepreneurial innovation (the agency), whereas the mononuclear case involves the spread of diffusion agencies without entrepreneurial adoption.