This paper is a literature review of various aspects of the wear of occluding tooth surfaces. It presents classification and terminology of occlusal tooth wear, and discusses etiology and differential diagnosis. It may be difficult to differentiate among abrasion, attrition, and erosion because there is nearly always a combination of the various processes. These processes of wear are described, and the in vitro and in vivo wear of some restorative materials is discussed. Treatment of severe tooth wear is considered difficult; prophylactic measures are therefore important. Some guidelines for restorative treatment of patients with extensive occlusal tooth wear are given, with special emphasis on the type of treatment, the vertical dimension of occlusion, the space available, and choice of material for the restorations.