The efficiency of two kinds of block appointment system for the following-up patient clinic was analyzed using an emulation technique. The data were obtained from the survey in Osaka Adult disease Center. In the system[A], scheduled patients are consulted in the sequence of arrival, but the priority of scheduled patients who arrive late is made lower than that of unscheduled patients. In the system[B], the sequence of consultation is fixed by the appointment table, but scheduled patients who are late will be consulted by the order of arrival and will not have lower priority than unscheduled patients. The advantages of the system[B]were suggested in the emulation studies.