Abstract: The metallothermic reduction of magnesium oxide to magnesium by means of a metallic reducing agent in a reaction zone at elevated temperature in the presence of a molten oxidic slag, wherein the product magnesium is vaporized and evolved from the slag into a substantially static atmosphere of inert gas and passes predominately by diffusion through the inert gas from the reaction zone to a condensation zone and is collected. As a result, not only is it possible to operate the process at a higher absolute pressure than heretofore, but also, unexpectedly, the magnesium product obtained is relatively pure as compared with commercial magnesium, and contains impurities, notably silicon, in low concentration.