The wear behaviour of a-C:H coatings in ambient air up to maximum temperatures of 300 degrees C is reported. A simultaneous tribological and thermal load was imposed using a low-amplitude oscillatory sliding test in combination with a heatable specimen holder. The investigation showed that the tribological behaviour of the a-C:H coatings changed considerably at elevated temperatures: the coefficient of friction decreased and the wear scars became larger and deeper, indicating a more severe wear process at elevated temperatures. Under the present test conditions tribological behaviour started to change around 100 degrees C. On previously annealed samples, however, the wear properties at room temperature remained stable up to annealing temperatures of 300 degrees C. The temperature dependent wear behaviour of diamond-like carbon has been linked to the surface properties of these materials which become modified at relatively low temperatures where bulk properties are known to remain unchanged. (C) 1998 Elsevier Science S.A.