An analysis is presented of the Illinois Public Community College Unit Cost Study for Fiscal Year (FY) 1980, an annual study using basic enrollment and cost data supplied by college for each instructional area offered. After introductory material, including study highlights and a glossary of terms, district and school data are provided on net instructional cost, full instructional cost (including building repair and depreciation), and total institutional cost (including instructional, research, and public service costs) per student credit hour. Information is then provided on unit costs for educational support services and other indirect costs under seven categories; i.e., academic administration and planning, learning resources, student services, data processing, general administration, auxiliary services, and general institutional support. Next, net instructional cost per student credit hour is analyzed by district for the following instructional categories: general academic and baccalaureate, business and public services technologies, technical occupations, health technologies, remedial development, adult basic/secondary education, and general studies. Finally, instructional costs for FY 1980 are compared with costs for the previous ten years and sample unit costs are provided by instructional area and cost category. Appendices offer data on total cost per college by functions and cost category and instructions for completing the 1980 unit cost study. (HB)