The effect of surface treatment [rare earth solution (RES) and air oxidation] of carbon fibers (CFs) on the mechanical and tribological properties of carbon fiber-reinforced polyimide (CF/PI) composites was comparatively investigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fiber and PI matrix. Thus, the flexural strength and wear resistance were significantly improved. The RES surface treatment is superior to air oxidation treatment in promoting interfacial adhesion between carbon fiber and PI matrix. (C) 2007 Wiley Periodicals, Inc.