Thermodynamical considerations on the vapor‐phase growth of whisker and platelet crystals of &agr;‐Al2O3by the oxidation of aluminum lead to the conclusion that the vapor‐phase mass transport is probably due to the suboxide Al2O and not AlO as previously suggested. Electron microscope observations confirm the optical evidence that spiral growth steps do not occur on the (0001) surfaces of Al2O3crystals grown in this way.