Important applications of fast fluidized beds include reactors where liquid feed is sprayed into the co-current flow of solid particles and gas. When the gas and the solid particles are superheated relative to the saturation temperature of the liquid, the liquid drops evaporate at a rate governed by interfacial heat and mass transfer. This article describes an experimental method to determine the rate of liquid evaporation in such three-phase systems. Analogous experiments were carried out with liquid nitrogen evaporating in superheated beds of sand particles and air.