Experiments on the spray of water have been carried out using a rotating cup in a chamber of 120 cm in diameter. The feed rate of water was varied from 3 to 10 kg/h and the rotation speed of the cup from 10,000 to 20,000 rpm. Measured drop sizes were compared with those predicted by empirical equations; there existed considerable discrepancies between experimental data and predicted values. In the presence of a swirling air in the chamber, the water drops ejected from the cup moved toward the wall as they fall down, following the main stream of the air. Some of the drops moved toward the center of the chamber by a recirculating air flow. The drop size increased in the axial direction toward the bottom, probably due to coalescence between water drios. The turbulence of the air and the extesion of residence time of the drops by the swirling action of the air must have increased the chance of the coalescence.