Vapor phase lubrication has been demonstrated using a conventional four-ball wear Lester run at 370°C using M50 hot hardness steel ball bearings. The four-ball wear tester was modified to control both the temperature and the environment surrounding the ball pot and spindle. The lubricant in all cases comprised a homogeneous gas phase mixture of nitrogen and phosphate ester vapors. The two phosphate esters used were tributyl phosphate (TBP) and tricresyl phosphate (TCP). The volume percent phosphate ester vapor in nitrogen ranged from 0.10 to 6.0 percent. The minimum temperature of the four balls was maintained at 370°C which was always at least 50°C higher than the temperature of the homogeneous vapors delivered so that there was no possibility of vapor condensation on the wear contacts.