The evolution of industrial "rms has recently passed from a strong growth phase to a phase where there is a greater complexi"cation of products: widening the range of products in catalogues, diversi"cation and personalization of models. The current trend is to use, with production management techniques such as classical manufacturing resource planning (MRP2), the concept of two level master production schedule (MPS), using planning bills with percentages indicating the probability that such or such an option will be used. This necessitates, however, the implementation of a rigorous approach to continuous improvement using just in time (JiT) and total quality (TQ) concepts. In the "rst part of our paper we discuss principles of operating two level MPS; secondly, we analyze these e!ects on management and organization. Our paper is based on a case study. 2000 Elsevier Science B.V. All rights reserved.