Study Objectives: To delineate excessive supply preparation in the operating rooms (ORs) of Yale-New Haven Hospital, and to measure the reduction in such overage as a result of nursing and administration cost-containment efforts. Design: Before and after trial. Setting: Inpatient ORs of Yale-New Haven Hospital. Interventions: After the initial documentation of overage, several cost-containment measures were instituted, including nursing education, review of overage data, and updating of surgical request lists. Measurements and Main Results: The hospital cost of case-specific overage generated by all surgical procedures performed during two 2.5-month periods in 1992 and 1994 (before and after the interventions) were compared. One-thousand three hundred eighteen cases in 1992 were compared with 1,367 cases in 1994. A 45% reduction in mean per case overage occurred between the two assessment periods. Extrapolation of the data to the incidence of similar cases throughout the United States projected a comparable savings. Conclusions: Efforts to increase the efficiency of OR supply management can be measured, in part, by overage evaluation, which can serve as a resource for focusing efforts at cost-containment.