The microstructure of wear debris originating in sliding tests from pure metals which form stable metal oxides with the rutile structure (like: manganese, tin and titanium)has been investigated by analytical TEM. The influence of the oxidation reaction on the formation of either amorphous or nanocrystalline debris was studied. Data on wear debris generated on manganese and tin are presented and compared with observations on debris from pure titanium. These observations support the thesis that:the debris structure is depending on the oxidation kinetics. Evidence is given for the crystallization of amorphous debris due to continuous oxidation during wear. (C) 1999 Elsevier Science S.A. All rights reserved.