In electro–mechanical engineering manufacturing, a professional 'make' versus 'buy' policy generally results in a large percentage being purchased from outside suppliers. To achieve the full benefit from competitive, modern, manufacturing systems engineering methods, these methods must extend into relationships with suppliers, the elimination of bad supplier practices and to developments of manufacturing systems improvements in suppliers' factories. This is of particular importance in supporting Just–in–Time and Total Quality approaches aimed at reducing product costs and improving reliability of supplies. Systems Engineering methodologies are applied to the design of good supplier practices and the management and monitoring of supplier relationships and rationalization. These also focus on the need far new organizational approaches to clarify responsibilities and simplify procedures. In turn, this leads to a need for a realistic mix of measures of performance which reflect contemporary competitive business targets at all levels.