This study involved the development and use of a cost model to assess the economic consequences of the introduction of a year-round school (YRS) program. The cost model has two components. First, a comprehensive accounting procedure details the costs unique to a year-round calendar and estimates the costs that would have been incurred if the school had remained on a traditional calendar. Second, an interactive computer program permits sensitivity analysis. The cost analysis model was first used to determine the financial impacts of the YRS program implemented in the Pajaro Valley Unified School District (California). The model revealed a savings of $150,000 or 4.1 percent of the district's total per pupil expenditure. When the model was used in six other California school districts, savings ranged from $9,000 to $251,000. Usually the YRS program results in costs savings of 4-5 percent. The diversity of results may be due to some schools making programmatic changes as a result of the YRS program. Thus anticipated costs savings will shrink dramatically unless the schedule change is managed judiciously. Overall, the results of the analysis indicate that careful implementation of a YRS program can result in substantial cost savings. (Author/JM)