X-ray reflection intensities were measured with a diffractometer on Powder specimens of NiO, CoO and MnO, of particle size less than about 5 µ with MoK α ,CuK α FeK α and CrK α . By a scaling procedure, the absolute values of the experimental structure factors were derived. The temperature factors of individual ions were estimated by three dimensional difference Fourier syntheses. The factors obtained were B Ni =0.63 Å 2 and B O =0.41 Å 2 for NiO, B Co =0.52 Å 2 and B O =0.48 Å 2 for CoO and B Mn =0.88 Å 2 and B O =0.66 Å 2 for MnO. It is found that the electron Distribution in the three oxides is very similar to each other, and that the electron density near the center of [111] direction is smaller beyond the limit of experimental errors than that of the theoretical calculations for the spherical free ion.