Films have been prepared by reactive sputtering in an oxygen‐containing glow discharge, by ion‐beam sputtering in an accelerator, and by anodizing with an ethylene‐glycol‐based electrolyte. The sputtered films were amorphous if deposited on or Ta at temperatures from −100° to +200°C, though were crystalline if deposited on . The anodic films were variously crystalline or microcrystalline, though clearly nonamorphous. The crystallization temperatures ranged from i.e., rutile type). The thickness (d) of the reactively sputtered films was estimated by noting the interference colors when using a Ta substrate and assuming the validity of the relation where is the index of refraction. The thickness of the anodic films was estimated by sputtering the films with 20‐keV Kr ions until metal was exposed and noting the weight change. The anodization of Sn has a rather low efficiency (4–21%), and this could be shown to be due to electronic conduction rather than to dissolution.