An ultrahigh vacuum (UHV) force measurement device has been used to study friction between Cu(111) surfaces separated by adsorbed films of 2,2,2-trifluoroethanol (CF3CH2OH) ranging in coverage from 0 to 15 monolayers (ML). The instrument is designed such that both samples may be prepared and characterized under UHV conditions and then brought into contact and sheared relative to one another without exposure to atmosphere. Both shear and normal forces generated at the metal-metal interface are measured simultaneously during sliding. The shear behavior of the clean Cu(111)-Cu(111) interface is characterized by high, erratic friction forces with a static friction coefficient of mu(s) = 4.6 +/- 1.1. The presence of adsorbed trifluoroethanol at the interface does not affect the friction coefficient until the trifluoroethanol coverage reaches approximately 1 ML, after which the friction coefficient is significantly reduced. The static friction coefficient gradually decreases to a limiting value of mu(s) = 0.38 +/- 0.07 at trifluoroethanol coverages greater than approximately 8 ML. The friction coefficient was found to be independent of normal force (F-n) and sliding velocity over the ranges accessible with the UHV tribometer (F-n = 2-80 mN, velocity = 0.5-200 mu m/s).