Advanced surgical technology demands more precise, meticulous, and time-consuming procedures. In addition, the patient's preference of tertiary health providers makes over crowding of the University Hospitals. Therefore, it has been necessary to maximize utilization of the operating room of such hospitals to accommodate these requirements. This study, targeting 1,302 surgical cases performed in 22 operating rooms at a university hospital in Seoul from October 8 to November 1, 2001, analyzed reasons for delay, and factors that caused delayed use of operating rooms. This study also assessed that the rate of operating room use would increase if the sources for possible reform were improved. 1. Among total of 1,302 cases of surgery, the incidence of surgeries in which there were no time delays and no factors for delay were discovered is 71.4% or 930 cases: the incidence in which surgeries were delayed was 28.6% or 372 cases. 2. As results of logistic regression for delay, procedures involving women were delayed 1.4 times more frequently than those of men. Compared to Department A, Department B was 1.8 times more likely to be delayed, and Department H was 0.4 times less likely to be delayed. Regional anesthesia was 2.4 times more likely to be delayed than general anesthesia, and surgeries that PCA was applied were 0.6 times less likely to be delayed than those when it was not. Surgeries performed on the Thursday were 1.7 times more likely to be delayed than those performed on the Monday. Compared to surgeries performed between 07:00-07:59, those performed between 08:00-08:29 were 4.3 times higher. 3. The reasons for delay were related to surgeon, surgical department, patient, anesthesia, administrative system, sick ward, and support services. Among these, 5,755 minutes for 276 delayed cases could be resolved easily, and resolving delays of 3,320 minutes for 131 cases would be more difficult. Among the causes for delay that could be improved, delays due to patient's transfer and surgeon's factor were the most common, 21.6% and 17.4% respectively. 4. If resolvable delays are improved, pre-anesthesia room is administered, and regional anesthesia and PCA are done ahead of time, use of emergency operating rooms will increase, we can increase overall utilization by 4.09%, we will save 744 minutes a day, we can reduce the time the operation room is used after 4 PM by 35%, and we can resolve the operation cancellations due to insufficient operating rooms. For the increase in the use of operating rooms, we need to maximally decrease the delays that could be improved, by allocating block time based on used totals hours of elective cases, giving accurate information on surgery schedule, voluntary cooperation by staff participating in surgeries in reducing delay time, and the hospital management's will to improve delay.