A study on the wear behavior of an ultra high molecular weight polyethylene (UHMWPE) sliding on the discs made of two types of ceramics was conducted by a ring-on-disc reciprocal wear test. The properties including friction coefficient, wear factor, debris, and transfer film of UHMWPE were evaluated and correspondent to the variables in the wear tests. Those variables included type of disc materials (zirconia and alumina), lubricants, types of contact face of UHMWPE rings, and surface roughness of discs. The results indicated that the friction coefficient and wear factor were closely controlled by the roughness of the disc. The wear mechanisms of UHMWPE sliding on zirconia could be categorized by two types of surfaces differentiated by a critical roughness (R-a) of 0.10 mum. The effects of debris and transfer film (i.e. third body effect) were investigated. By reducing the initial roughness of UHMWPE, pre-coating a transfer film onto the disc, and using saline as a lubricant can slightly reduce the friction coefficient, and improve the wear factor of the UHMWPE on ZrO2 disc. (C) 2004 Elsevier B.V. All rights reserved.