In relation to their potential genotoxic properties, the ability of inorganic particles to induce activated species of oxygen with strong oxidative properties can be studied by various methods. In this study the oxidative surface properties of 10 different natural and synthetic mineral fibres were investigated by: (1) an electron paramagnetic resonance technique in which formate was used to trap oxidative species; and (2) a high performance liquid chromatography (HPLC) based method in which deoxyguanosine was used as a trapping agent and the formation of 8-hydroxy-deoxyguanosine (8 OHdG) was analysed. Ground iron-containing fibres such as crocidolite and amosite were the most reactive, whereas fibres without iron--for example, ceramic fibres, xonotlite, and Tismo L--were completely inactive. A good correlation was found when the results from the two methods were compared (r = 0.86).