Thermoplastics and other organic polymeric materials exhibit numerous characteristics that make them advantageous as components in tribological applications. One of the most important factors in determining the wear characteristics of polymers is the counterface topography. A recently developed semi-crystalline aromatic thermoplastic, poly(aryl-ether-ether-ketone) (PEEK), has been investigated under dry, lightly loaded sliding conditions against a low carbon steel counterface of varying surface topography. A test apparatus was designed and constructed for testing specimens in the three-pin-on-disk configuration. Surface characterization parameters of the steel counterfaces were obtained using a profilometer interfaced with a personal computer. The experimental results showed that the wear of PEEK is dependent on the counterface topography. Against rough counterfaces, PEEK exhibited the highest relative wear. Wear of PEEK decreased as counterface roughness decreased, and then increased again as the steel counterface became very smooth. Wear debris from the tests was observed in a scanning electron microscope (SEM) and revealed various forms depending on the steel counterface topography. Against very smooth surfaces, wear particles were relatively large thin sheets. Against rough surfaces, wear debris was considerably smaller and more fragmented. When wear exhibits a relative minima, debris accumulated under the PEEK pin in a sheet like form. Attempts were made to model potential failure mechanisms of PEEK in the smooth and rough counterface wear regimes. A PEEK/carbon fiber composite material was tested under similar experimental conditions, to reveal the effects of fiber reinforcement on the wear rate and wear mechanisms. SEM analysis revealed that the morphology of the worn PEEK composite surfaces and wear debris was distinct from that of the non-reinforced PEEK.