Results obtained in pin-on-ring tests of hardened-and-tempered steel are analysed. It is shown that the rate of wear can be related to an 'index of wear intensity'. This index is derived from the external variables of load, sliding speed and the hardness of the two components of the sliding pair. It may be regarded as a measure of the conditions that prevail in the contact zone. (C) 1997 Elsevier Science S.A.