Abstract The component fatty acids of a specimen of unbleached Japan wax, which contains no kernel oil, have been examined. In agreement with the description in fat literature, palmitic acid is, of course, the main component. Myristic acid and the lower homologues appear not to be present; volatile lower acids stated to occur in Japan wax by old investigators are undoubtedly decomposition products formed by bleaching process. On the other hand, stearic and arachidic acids occur in appreciable proportions. The unsaturated acids consist mostly of oleic acid. A small proportion of linolic acid is present. Hexadecenoic and linolenic acids are probably not present. It is difficult to mention the quantitative proportion of the individual acids, but rough approximation would be as follows: Palmitic acid 77%, stearic and arachidic acids 5%, oleic acid 12%, linolic acid small amount (less than 1%), dibasic acids 6%. The above proportion of stearic and arachidic acids would be rather high; in their relative amounts the former seems to predominate. It is interesting to observe that whereas myristic acid can not be detected in Japan wax obtained from Rhus succedanea, it occurs abundantly in the wax of “Tsutaurushi”, Rhus toxicodendron, var. vulgaris, a viny shrub belonging to the same genus Rhus. The free acids in Japan wax have nearly the same composition as the mixed acids of the wax, but oleic acid is present in a far larger proportion.