The first part of this report is a review of information derived from tests and actual fires on the amounts of water necessary to extinguish fires in rooms. The second part of the report describes experiments made at the Joint Fire Research Organization in which the extinguishing capacity of sprays and jets have been studied under various conditions. At low rates of flow the amount of water required is the same with sprays as with jets and it increases with increasing rate of flow. This increase, however, is much less marked with sprays. The degree of manoeuvreability of the spray or jet affects the rapidity of extinction less with sprays than with jets.