The effect of PTFE on the tribological behavior of polymers in rolling sliding contact has been investigated. The two most widely used polymers - nylon 66 and polyacetal-were used as the base material. Tests were conducted over a wide range of running conditions using a twin disc rolling-sliding test rig for both the unfilled materials and for the base materials filled with 20 wt% PTFE. The experimental results showed that the friction and wear performance of the PTFE filled polymers was superior to that of the unfilled polymers. In addition the surface cracking that was found in unfilled PA66 and was thought to be responsible for premature fracture of components such as gear teeth was suppressed by the PTFE. It is suggested that a combination of high surface temperature and high surface tensile stress, produced by friction, is required to initiate these cracks and that PTFE, by reducing friction, inhibits crack formation.