It was found in this investigation that an alloying reaction occurred wherever and whenever clean metallic surfaces of aluminum and uranium were brought into contact within the temperature range of 250OC to 450oC. Anodization of the aluminum surface prevented the alloying reaction. The effects of temperature. aluminum purity, and pressure between the metal surfaces on the alloying reaction were studied qualitatively. The alloying reaction produced UAl3, which appeared to be formed by the diffusion of the uranium through the UAl3 layer. (MM).