A system to determine cost effectiveness of class size should be based on both budgeted and actual expenditures and credit hours at the individual course section level. These two factors, in combination, are often expressed as cost per credit hour, and this statistic forms the primary means of evaluating planned "inputs" against actual "outputs." For purposes of determining a cost-effective class size, it is not as important that fewer dollars were spent than were budgeted, or that credit hours generated exceeded or fell short of those planned. Rather, it is the control of the proportional relationship between these two factors which, if attained, can improve efficiency. Generally, the relationship between expenditures and credit hours should be close. However, budgeting these factors at the section level is not likely to increase planning accuracy--many enrollment influences are beyond the control of planners. Additionally, several problems exist in implementing this type of cost effectiveness analysis. The cost of budgeting at the section level is likely to be prohibitive, and factors such as contractual obligations with the faculty, the nature and fluctuation of student enrollments, and student preferences for classes may all impair administrative ability to obtain optimum class sizes. Hypothetical cases are used to demonstrate the system, and an appendix considers the problems of assigning indirect costs at the section level. (DR)