Publisher Summary Material requirements planning (MRP)-based systems provide a framework for managing production, and they serve as extensive information systems for production planning and control. This chapter discusses four main areas in which MRP systems typically have shortcomings and where supplementary models can provide effective decisions support. The first of these dealt with lot sizing. Heuristic procedures for single-level lot sizing have been tested extensively, and discernable conclusions have emerged. The second area dealt with master scheduling, where two model-based perspectives were presented. The third area dealt with capacity planning, where models can go beyond the MRP system response of merely signalling violations. Input/Output models provide some understanding of the relationship between work center capacities and production lead times. The fourth area dealt with buffering techniques. Most of the attention by model builders has been focused on the analysis of demand uncertainty, and in particular, on techniques for hedging with safety stock within the product structure.