Microcrystalline powder of boron phosphide has been synthesized by self-propagating hightemperature reaction of boron phosphate and metallic magnesium: BPO 4 + 4Mg = BP + 4MgO using the method described earlier . According to X-ray diffraction study (TEXT 3000 Inel, CuKα1 radiation) the sample is well-crystallized sphalerite BP with lattice parameter a = 0.45356(9) nm, which was close to the literature value 0.4538(2) nm . The amount of B 12 P 2 boron subphosphide impurity caused by a partial decomposition of as-forming BP due to a high local temperatures in the reaction mixture did not exceed 1 vol.%. Microstructure of boron phosphide has been studied by high-resolution transmission electron microscopy (HRTEM) using JEM-2010 microscope with energy dispersive X-ray spectroscopy (EDS) attachment.