The endurance lives of rf sputtered MoS2lubricant films are severely degraded by exposure to high humidity environments prior to wear testing. Surface chemical and electron microscopic analyses show that the degraded films are oxidized to form MoO3and that the oxidation rate is a function of the orientation of the crystallites composing the films before any run-in or burnishing activity. If the crystallites are arranged with their basal planes parallel to the substrate surface, the films have lower reactivity (good stability) and longer endurance lives than film with randomly oriented crystallites. The results of surface analyses and wear tests are presented to support these observations.