Maintenance and renewal costs can have different definitions in various countries, and it may be misleading to compare the costs of each of these two categories from one country to another if the definitions are not the same. This section aims at shedding some light on this issue through a precise definition of these two categories of work in France. Doing so implies to have a view on the policy and on the organizational structure of maintenance operations. Therefore we will first recall the organization of maintenance in France, then explain the maintenance policy hitherto implemented and the changes at work before setting the precise boarder between maintenance and renewal.