By the electron microprobe Kossel technique, an a-precipitate at a grain boundary of a Cu-45wt% Zn alloy was found to consist of only one crystal and the orientation relationship between the a precipitate and one of the grains beside the grain boundary was (110)β//(111)α and <111>β//<110>α. This is the same relationship as the case α a precipitates in β-phase grains. A little deviation from the exact coincidence of above orientation relationship was observed. The vacancy model for the production of a denuded zone in the same alloy was confirmed by a line scanning analyses using an electron microprobe. An effect or orientation differences was observed on the specimen current of the electron microprobe. This effect was attributed to a channelling phenomenon. The influence of ths channelling effect on quantitative analyses by electron microprobe was considered for the precipitated a-phase and matrix β-phase, and the massive a precipitates were found to consist of many crystallites having different orientations. From the lattice constant of the g-phase determined by the Kossel patterns, the concentration of zinc at the target point was obtained in good agreement with the value obtained by quantitative analyses using an electron microprobe. Thus, in some cases, the Kossel technique can be utilized for the quantitative analysis of a small portion without any corrections which are necessary In the case of electron microprobe.