This paper is concerned with the performance of alternative dampening procedures to cope with system nervousness in manufacturing firms that employ a material requirements planning (MRP) system. It presents three dampening procedures to reduce rescheduling frequency of open orders. These procedures arc compared using a simulation study. The results indicate that the performance of a dampening procedure depends upon the operating environments of manufacturing firms. The results also show that the reduction of system nervousness, as measured by the frequency of schedule disruptions, does not necessarily lead to a better system performance. It is the appropriate employment of a dampening procedure and lot-sizing rule that can contribute to the system improvement.