This new book will be useful not only to practising engineers and scientists, but also to advanced students interested in wear. It reviews our current understanding of the influence of microstructural elements and physical properties of materials (metals, polymers, ceramics and composites) on wear.The introductory chapters describe the relation between microstructure and mechanical properties of materials, surfaces in contact and the classification of wear processes. The following chapters are concerned with wear modes of great practical interest such as grooving wear, sliding wear, rolling-sliding wear and erosive wear. Our present understanding of abrasion, adhesion, surface fatigue and tribochemical reactions as the relevant wear mechanisms is discussed, and new wear models are presented. In addition to extensive experimental results, sketches have been widely used for clarifying the physical events.