It is necessary to predict the excess attenuation of road traffic noise by the buildings for the evaluation of `Environmental Quality Standards for Noise' at the areas facing roads . Three kinds of predicting methods have been proposed by the Acoustical Society of Japan and the authors. They have their own merits and demerits, and we need to understand them well when applying these methods to the evaluation of the Standards. Excess attenuation predicted by these methods is calculated by computer and the simulated results are compared. And the feature of each method is made clear, and the problems when applying them to the evaluation of the Standards are pointed out.