Abstract The supply and demand of drinking water has become unbalanced in many places due to population growth and changes in weather conditions. About 2000 million people do not have a stable source of drinking water at present. This shortage of drinking water affects many countries in the third world, which also lack conventional energy sources. As these countries usually have salt water resources and a high level of solar insolation which could be used to produce drinking water from brackish or seawater, the Spanish research institution CIEMAT (Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas) and the German DLR (Deutsche Forschungsanstalt fur Luft- und Raumfahrt e.V.) are promoting solar brackish and seawater desalination R&D in the so-called Solar Thermal Desalination (STD) Project. The STD Project forms part of the Industrial Solar Energy Applications Investigation Program, now being carried out at the Plataforma Solar de Almeria (PSA), a solar energy research center located in Southern Spain. Project objectives and current status are described in this paper, together with some preliminary results of first phase test campaign evaluation and an overview of system improvements to be implemented in the second phase of the project.