For seven bronzes of different composition and structure the ability to form boundary lubricant films is described in terms of a transition temperature at which the mild (abrasive) wear process changes into a severe (adhesive) one. Addition of lead or phosphorus to Cu 6Sn lowers this transition temperature considerably. Probably the formation in the bronze of finely dispersed tin-oxide particles is beneficial, surplus phosphorus inhibiting the formation of such particles. Oxidationin situdoes not improve the adsorption properties of the surface. Effective boundary films are formed on a thin transferred bronze film on the shaft, rather than on the bearing surface itself.Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE International Lubrication Conference held in New York City, October 9–12, 1972