Research into the extinction of fire of solid and liquid fuels by plain water has been reviewed. Properties of water sprays and of the fires themsel ves that influence the performance of sprays as extinguishing agents are outlined. The results of basic investigations which have yielded data which are of assistance to quantifying extinction processes and of empirical investigations designed to provide information directly applicable to practical problems have been briefly summarised. Simple quanti tati ve approaches to two forms of extinction for which basic data exists i.e. extinction of the flames by spray and cooling the fuel to the firepoint are outlined. The approach to extinction by cooling also points to an approach for deciding under which conditions stable flaming may be formed on the whole of a fuel surface in the absence of spray. Areas for future research are indicated.