The micromechanical behavior of MoS 2 acting as a solid lubricant and the effects of humidity thereon have been studied in moist nitrogen through simultaneous measurements of momentary friction and electrical contact resistance in the so-called hoop apparatus. The sliding couple consisted of a gold-plated copper substrate (the circumferential track inside the hoop) lubricated with a burnished MoS 2 film, and a slider in the form of three bundles of 50 μn thick gold-plated copper fibers. This geometry permits indirect detailed studies of the film conditions at the contact spots, since both the friction and the contact resistance are exclusively determined by the film. All measurements were found to be reversible, with the friction coefficient and contact resistance depending in a somewhat complex manner on average sliding speed between 0.05 and 3.0 cm s −1, load between 0.5 N and 8 N, and relative humidity between 20% and 90%. The data indicate that adsorbed moisture causes the MoS 2 film to mechanically soften and that the film is partly pushed ahead and to the sides of moving contact spots. As a result, the film thickness between the contact spots, presumably with the basal plane preferentially parallel to the interface, decreases with humidity but increases slightly with sliding speed and contact spot size, i. e. load. Accordingly, the major part of the coefficient of friction, namely μ o≈0.1 through distributed shearing of the MoS 2 film parallel to the basal plane, is little affected by any of the variables, but the contribution due to film plowing rises with increasing humidity from zero up to μ p≈0.1. The contact resistance, by contrast, varies through almost two orders of magnitude. It increases much faster than proportional with the film thickness at the a-spots, due to a strong increase of the MoS 2 resistivity with film thickness, on account of a semiconductor effect.