Tests have been carried out to determine the effect of three water sprays of different drop sizes on six liquid fires. The liquids were alcohol, benzole, petrol, kerosine, gas oil and transformer oil. The sprays had a rate of flow to the fire area of 1.6 g cm-2min-1 and the drop sizes were 0.28, 0.39, 0.49 mm. It was found that the finest spray was best for extinguishing the more volatile liquids, but the coarsest spray was best for the less volatile liquids. The results suggest that the main mechanisms of extinction of the fire were (1) cooling the liquid to below the firepoint, (2) smothering the flame by formation of steam at the hot burning liquid, (3) extinction of the flame either by steam formation in the flame or cooling, (4) for alcohol, by dilution. The finest spray used, which was found effective against volatile liquids, is finer than fire fighting sprays in general use. Methods of reducing the drop size of fire fighting sprays are discussed.