Water is becoming day by day a more precious and even scarce natural resource. In Europe, water shortage or water stress is notable in countries such as Spain, Turkey, Italy, Greece, etc., where rainfalls are few, irregular and inconsistent. In order to improve the use of the Spanish hydrologic resources and to satisfy the higher water demand due to, not only tourism but also agriculture and increased population, the Spanish Government has been promoting over the last years different strategies. In July 2005, a new Act (National Hydrologic Plan) was passed, which included more than one hundred immediate points of action to improve the existing water-related infrastructures and to construct new desalination plants. In addition, in December 2007, a Royal Decree was approved in order to regulate and to promote water reuse applications in the country. Reverse Osmosis is currently taking a fundamental role in seawater and brackish water desalination as well as in water reuse installations. in this paper. the current situation of Spain in terms of water resources is reviewed, the performance of some Reverse Osmosis plants already in operation is documented and the latest key innovations of Reverse Osmosis such as recently developed modules, new configurations and modules with larger diameter are described. (C) 2009 Elsevier B.V. All rights reserved.