This paper addresses basic issues germane to selecting materials for
high-temperature aggressive environments. The overview provides first-choice options for dealing with corrosive conditions that extend beyond clean oxidation, including aggressive fluids and molten salts. Examples of material failures in various complex environments are included. Keywords: high-temperature corrosion, sulfidation, hot corrosion, halogenation, carburization, metal dusting, hot salt corrosion, vanadic slags, molten salts, molten glasses, materials selection.