Sliding friction experiments involving copper and Cu-Be alloy plates in contact with copper, Cu-Be alloy, steel and titanium alloy sliders were performed in air and vacuum. Micro-hardness and metallographic examination of plate and slider interface suggests friction and wear by the adhesive friction mechanism with prow formation. Transfer of strain-hardened metal wear debris across the sliding interface leas observed. The friction coefficient and the prow size generally increased in vacuum.Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Atlantic City, New Jersey. October 8–10. 1968.