Potential clients for centralized school district organizations with formal responsibilities for research and evaluation include societies, federal and state governments, boards of education, superintendents, other administrators, principals, and teachers. Not all clients are equal. An historical review of the evaluation literature supports the proposition that some research and evaluation unit (R&E) clients are served more directly than others; that this service to particular clients is in response to their demands; and that service to all clients is shaped by the demands of the most direct clients. Historically, superintendents were the most directly served clients; in responding to their administrative needs, R&E units engaged primarily in data collection activities. Despite federal and state evaluation requirements mandated by the Elementary and Secondary Act R&E units may still be engaged primarily in data collection activities (such as the reporting of norm referenced test scores) rather than in evaluation activities. It is likely that instructional clients such as teachers and project directors will be less directly served than administrative clients. (Author/CP)