The practice of cost-benefit analysis (CBA) has a long tradition in France, dating back to Dupuit (1849), but is still a topical subject. This practice is in fact the result of the combination of economic theory and decision processes regarding project choices. Both of these are constantly changing: advances and progress in the theory mean that the technical methods and tools used are constantly improving, while changes to decision processes and institutional organisations are transforming evaluation requirements. In some countries, the process of constant change has been very fast indeed. This is currently true in France, where major transformations are occurring. We are now leaving a period during which the doctrine was based on the strict application of…