The wear and friction properties of poly (ether-ether-ketone) (PEEK) reinforced with 0-33 vol % (60 wt %) micron size Al2O3 composites were evaluated at a sliding speed of 1.0 m/s and nominal pressure from 0.5 to 1.25 MPa under dry sliding conditions using a pin-on-disk wear tester. The wear resistance of the pure PEEK is 10-fold higher than that of mild steel under the similar test condition. It is improved to 18-fold as compared with mild steel at 3.5 vol % Al2O3 content. The improvement in wear properties may be attributed to the thin, tenacious, and coherent transfer film formed between the steel countersur-face and composite pin. However, the wear resistance of PEEK containing above 3.5 vol % Al2O3 was deteriorated, despite their higher hardness and stiffness as compared with that of composites containing lower Al2O3 content. This is attributed to the formation of thick and noncoherent transfer film, which does not prevent the wear of the composites from hard asperities of countersurface. Moreover, hard Al2O3 particles present in transfer film act as third body wear mechanism. The coefficient of friction of the composites is higher than that of pure PEEK. SEM and optical microscopy have shown that wear of pure PEEK Occurs by the mechanism of adhesion mainly whereas of PEEK composites by microploughing and abrasion. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3379-3387, 2008