This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H-2 and O-2, and H-2 or O-2 evolution from an aqueous solution containing a sacrificial reagent. Many oxides consisting of metal cations with d(0) and d(10) configurations, metal (oxy) sulfide and metal (oxy) nitride photocatalysts have been reported, especially during the latest decade. The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials. Photocatalytic water splitting and H-2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references).