Uniform spherical MgF2 and cubic NaMgF3 particles were obtained by aging at 80 degrees C solutions containing NaF and MgCl2 in certain concentration ratios. The electrophoretic mobilities of these dispersions, determined in the presence of various excesses of F- ions, showed the particles to be positively charged. Thermal analysis and X-ray diffraction data indicated that MgF, spheres were formed by aggregation of microcrystallites, while NaMgF3 cubes were generated by diffusional growth, possibly as a result of the Ostwald ripening process.