The Angström-bar method has been modified and adapted to the measurement of thermal diffusivity of metals for temperatures ranging from 300 to 1050 F. A small, sinusoidal temperature fluctuation is superimposed on the mean temperature of a thin-wall tubular specimen by means of simultaneous heating and cooling at one end. Thermal diffusivity was calculated from the phase shift and amplitude ratio of the temperature waves determined at two measuring stations. The effect of possible surface heat loss is considered. Measurements were made on AISI 1018, 1045, 3140 steels, and 1.1 per cent carbon tool steel. Results obtained for electrolytic tough-pitch copper and 2S aluminum showed good agreement with a recent theory of Storm concerning the variation of thermal diffusivity of simple metals with temperature.