The mokume technique in Japanese metalworking consists of joining alternate thin layers of different metals, deforming the assembly, cutting the surface flat so that it is intersected by the joined layers, and finally developing a wood-grain pattern by a patination process that gives the two metals different colors. Sections from objects made in this way were an in the electron microprobe, and traces of the elemental composition across the sections are presented. Diffusion profiles were developed from these results; joining of the altemate layers by solid-state diffusion could be distinguished from joining by a thin inter-layer of a third metal.