Frictional behaviors between mica surfaces have been investigated with the Surface Force Apparatus under various relative vapor pressures (RVP) of both water and cyclohexane. The dependence of frictional forces on RVP, particularly in the low RVP range, has been studied because the embryo of liquefaction and layering of molecules occurs in these conditions. The results of the measurements of kinetic shear stress as a function of sliding velocity at different RVP reveal the role of liquid condensed around the contact zone. A mechanism based on capillary condensation is proposed to explain the role of RVP on friction by adsorption of liquid layers on free mica surfaces and at contact.