Cu-Pb alloy bearings were collected from diesel engines actually operated in the United States and Japan, and a study was made of the damage to bearing overlays and linings. Results indicated exposure of compound layers produced by the diffusion of overlay components due to the complete removal of overlay from large segments of the bearing inner surface. There were many bearings in which the Pb had been last from the Cu-Pb alloy. Based on the above results, experiments were conducted in which a tester was used to recreate the damage conditions of the overlay and the lining. Then, based on observation and the results of regenerative tests, it was concluded that high temperatures and lubricating oil used over a long period had a great impact on damage.