Handicap has proved to be the most contentious and arguably most misunderstood concept of the International Classification of Impairments, Disabilities, and Handicaps (ICIDH). This paper reviews the definition and characteristics of handicap as presented in the original introduction to the ICIDH, and presents some of the alternative suggested definitions. Limitations in the way the original conceptual model for the consequences of disease was depicted have led to the development of alternative models which draw attention to the importance of external factors, particularly for the genesis of handicap. The nature of these external factors and the implications of alternative models for the testing of the conceptual framework are discussed. The expression of handicap as a product of an interaction of a person with impairment and disability and the environment draws attention to the options available for the decrease of handicap through the modification of the environment, and not only by attempting to ameliorate the impairment or disability.