Abstract
The World Heath Organisation is in the process of revising the International Classification of Impairments, Disabilities and Handicaps (ICIDH). This paper describes the background to the ICIDH and the new features of the revised classification in relation to its aims and applications. The ICIDH has been extensively used in prevalence studies of disability and to measure the effectiveness of rehabilitation and examples of some of these studies are cited. The paper concludes with the plans for the future development of the ICIDH and the particular problems in translating the underlying concepts into assessment instruments that can provide valid and reliable data for research and statistical purposes including comparative studies.