Hydrogen appears as a good candidate for the chemical storage of solar energy. Water splitting using sunlight should be achieved with the best possible efficiency and in an economic way. Several approaches are considered, including photovoltaic cells to drive conventional electrolysis and photoelectrochemical cells. In addition, the production of hydrogen from sea water with the formation of chlorine instead of oxygen and the production of hydrogen coupled with the photooxydation of organic pollutants are addressed. Analysis of problems relevant to these various possibilities will be presented as well as the work-plan of the IEA's Hydrogen programme devoted to this question.