A method used to determine the thermal diffusivity of ceramic materials is discussed. This technique uses the readings from at least three equally spaced thermocouples inserted in either powdered or bulk samples of the ceramic material. The method requires that a transient, one-dimensional heat flow, either by heating or cooling, is established in the sample. The values of thermal diffusivity obtained by the present method yield reasonable results in bulk samples of insulating silica blankets and in samples of powdered magnesia.