This paper describes and analyses the PES programme developed and implemented by Vittel (Nestlé Waters) in north-eastern France. In order to address the risk of nitrate contamination caused by agricultural intensification in the aquifer, the world leader in the mineral water bottling business is financing farmers in the catchment to change their farming practices and technology. The paper examines the methodology used by Vittel, and the tenyear process that was necessary to transform conflict into a successful partnership. The paper's main conclusion is that establishing PES is a very complex undertaking, one that requires the consideration of scientific but also social, economic, political, institutional, and power relationships. The ability to maintain farmers' income level at all times and finance all technological changes was an important element of success, but primary reasons for the programme's success were not financial. Trust-building through the creation of an intermediary institution (locally based and led by a "champion" sympathetic to the farmers' cause); the development of a long-term participatory process to identify alternative practices and a mutually acceptable set of incentives; the ability to link incentives to land tenure and debt cycle issues and to substitute the old technical and social support networks with new ones, were all fundamental conditions of success.