Maintenance is at the heart of any industrial enterprise. It is seen as a contributing function to production, justified by the gains in competitiveness and by the availability of equipment to increase production. It is therefore important to develop a strategy to improve this function and to promote the means to improve the performance of this activity by conducting, preferably on a regular basis, a diagnosis to determine the corresponding weaknesses and strengths.The "MEDIAT" diagnostic method, which we will introduce in this book, is the result of twenty years of experience in the field of maintenance management. It helps to guide companies wishing to diagnose their maintenance processes and/or know whether or not they are ready to implement computerized maintenance management by a "CMMS", an "ERP" ...