Computer simulation Used to Evaluate CapacityIn many systems, proper scheduling of the conveners ion can lead to better use of existing capacity. Sometimes a careful analysis reveals a greater output rate the than was thought possible. Such an analysis was performed at the university of Massachusetts, Health service Output clinic. The clinic waiting rooms were overcrowded and confusing and the professional staff felt overworked and harassed. During day few walk inpatients came and appointment patients failed to appear, physicians where sometime idle. On other days physicians were still seeing patients up to an hour part closing time. A team of analysis set out to find better ways t o use the existing capacity. Their strategy was to build a Monte carlo simulation model of the clinic and to use the model experimentally to improve the clinic operations. First they examined clinic records to estimate the demand on the system the number patient visits per week during regular clinic hours. The pattern of patient of patient arrivals was examined by day of week and by time of day. This pattern included both periods of slack and periods of very high patient loads. The analysis used the simulation model to test experimentally the effects of various patient scheduling policies.The recommendations of the simulation experiment were actually implemented at the clinic during the following year, and several improvements in its operations resulted. Patient waiting time was reduced: the number of patients seen by physicians increased more than13 percent: and the average time that a patient spent with a physician went up by 5 percent. The number of our physicians worked decreased by 5 percent. Less overtime was required , and staff morale improved. Clearly the clinic existing capacity increased because resources were scheduled and used more wisely.