This volume contains the selected papers of the first I.D.M.M.E. conference on 'Integrated Design and Manufacturing in Mechanical Engineering', held in Nantes from 15-17 April 1996. Its objective was to discuss the questions related to the definition of the optimal design and manufacturing processes and to their integration through coherent methodologies in adapted environments. The initiative of the Conference and the organization thereof, is mainly due to the efforts of the french PRIMECA group (Pool of Computer Resources for Mechanics) started eight years ago. We were able to attract the internationru community with the support of the International Institution for Production Engineering Research (C.I.R.P.). The conference brought together two hundred and fifty specialists from around the world. About ninety papers and twenty posters were presented covering three main topics : optimization and evaluation of the product design process, optimization and evaluation of the manufacturing systems and methodological aspects.