Fiscal year (FY) 1990 results of the annual unit cost study of the Illinois public community colleges are presented in this report, based on data on course offerings, enrollments, and costs provided by the colleges. After an initial summary overview, data and analyses are presented, including: net instructional unit cost for FY 1990 compared with previous years; net instructional unit cost since FY 1984; state average instructional unit cost since FY 1984; 1990 instructional unit cost; net instructional unit cost by cost categories; indirect instructional support unit cost; and net instructional unit cost by the seven instructional cost categories. Highlighted findings included the following: (1) in FY 1990, the state average net instructional unit cost for the 39 community college districts in Illinois was $116.16, an increase of 5.1% from FY 1989; (2) state averages for the cost categories comprising instructional unit costs were $44.12 for direct salaries, $8.56 for direct department cost, $1.74 for direct equipment cost, $45.61 for allocated indirect cost, $15.62 for operation and maintenance, and $0.51 for building rental; (3) state averages for support services included $10.34 for academic administration and planning, $4.62 for learning resources, $9.83 for student services, $3.42 for administrative data processing, $7.75 for general administration, $0.42 for auxiliary services (subsidy only) and $9.25 for general institutional cost; and (4) average unit costs ranged from a high of $177.65 for Health Occupational programs to a low of $83.68 for Adult Basic Education/Adult Secondary Education. A total expenditures report is appended. (GFW)