The results of the annual unit cost study of the Illinois public community colleges are presented for fiscal year (FY) 1988, based on data on course offerings, enrollments, and costs provided by the colleges. After an initial overview, data and analyses are presented showing net instructional unit costs for FY 1988 compared with previous years; net, full, and total instructional unit costs; net instructional unit costs by cost categories; indirect instructional support unit costs; net instructional unit costs by the seven instructional cost categories and by subject area; and unit cost comparisons. Highlighted findings include the following: (1) the FY 1988 state average net instructional unit cost in the 39 public community college districts in Illinois was $103.92; (2) this represented an increase of 4.1% over FY 1987's average of $99.82; (3) with respect to the six categories comprising instructional costs, direct salary costs averaged $40.07, direct department cost averaged $7.56, direct equipment costs averaged $1.09, allocated indirect cost averaged $39.82, operation and maintenance costs averaged $14.59, and building rental costs averaged $0.80; and (4) unit costs ranged from a high of $164.97 for health occupation courses to a low of $65.96 for adult basic education/adult secondary education courses. (AJL)