The aim here is to establish a classification framework to evaluate the currently available uncertainty dampening methods used in reducing scheduling instability in materials requirements planning (MRP) systems. Dampening methods can first be categorized as the local and global dampening methods in terms of the locality of uncertain events to be resolved. In terms of the nature of dampening methods, they can be considered as inventory- or information-orientated dampening methods. Local dampening methods can be farther classified by the ‘type’ of uncertainty (i.e. timing versus quantity) and the level in the bills of materials to which this method can be suitably applied. The major advantages and disadvantages of each method will be identified. Also, the operating conditions within which each method can be applied are discussed before future research directions are suggested.