A first draft of a School District-Census Geo-Reference File for Illinois for 1980 has been completed. In this file each census enumeration district or block group is matched with the appropriate school district or districts. Companion files have also been developed for community college districts, area vocational education districts, and for a limited number of attendance areas within selected school districts. The purposes, procedures, limitations, and results of this process are explained in this paper. The geo-reference file can be used to apply income and poverty data in the 1980 census to determine federal and state funding for school districts. The file can also be used to learn the needs of groups and the distribution of minorities; to forecast future enrollment; and to facilitate a wide range of research projects as well as the funding for such studies. The authors detail step-by-step procedures to account for each line of population and geographical information listed in the 1980 census. The procedures assign the proper proportion of each census area and its population to the appropriate school district. Limitations in the geo-reference file at this point are identified and preliminary measures for evaluating the accuracy of the file are described. A technical appendix describes the file and contains an order form. (Author/MLF)