The friction and wear behavior of polyimide (PI) composites reinforced with carbon nanotube (CNT) and polytetrafluoroethylene (PTFE) were comparatively evaluated under dry sliding, water-, oil- or alkali-lubricated condition. The wear mechanisms of the composites were also discussed. Results indicate that, when comparison with the dry friction situation, PI-based composites results lower friction coefficients and wear rates under oil-or alkali-lubricated condition. The lowest wear rate of the CNT/PTFE/PI composite is recorded as 1.2 x 10(-6) mm(3)/Nm during the composite sliding in alkali, which is only about 40% of the value sliding under dry friction condition. The worn surface of neat PI under dry sliding is characterized by severe adhesive wear, whereas abrasive wear is the main character for CNT/PTFE/PI composites. The worn surfaces of CNT/PTFE/PI composites sliding in oil or alkali lubricated condition are smoother than those under dry or water condition. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1574-1578, 2011