Problems of cost stall substantial implementation of computer-assisted instruction, (CAI) particularly for dispersed populations. This paper examines the problems inherent in providing CAI to scattered groups so that accurate estimates of the costs of different technologies (including satellites) which could deliver CAI to dispersed populations can be made and so that, on the basis of these costs, educators can make decisions about the allocation of their resources. The paper first outlines a CAI system capable of reaching dispersed populations without excessive costs (i.e., the system requires only 110 bits per second communications capability for each student terminal). This makes the service economically feasible. Next, models of several communications alternatives for the system are provided. The results of this modeling constitute approximate minimum cost communication designs for many configurations of population dispersal. Finally, some basic economic trade-offs and implementation alternatives are described which are relevant to educators who must decide whether or not to use CAI for certain student populations. (Author/PB)