The components of existing district instructional information systems are identified and illustrated by examples from field studies and descriptions of work with two districts in defining their instructional information systems and assigning costs. Instructional information systems are loosely organized methods of providing past and present information about student attainment and program evaluation. These are analyzed into eight components (five "core" and three "contributory"): (1) specified users, (2) specified uses, (3) specified types of information inputs/outputs, (4) specified information delivery procedures, (5) specified monitoring of system functioning and of system use, (6) training for users in data-based decision-making and implementation, (7) availability of resources to support action planning, and (8) availability or resources to support implementation. Elements of each component common to all eight districts under study are then listed, followed by three case studies of instructional information systems: a student achievement model, a school improvement model, and a staff development model. Then a three-step cost analysis procedure is described: (1) identifying the system to which costs are assigned, (2) identifying costs associated with the system, and (3) evaluating these costs. The paper concludes with an impact assessment procedure, focusing on the extent to which an instructional information system impinges on various stages of decision-making. (TE)