In this article, the author talks about the concept underlying the term metal retardation and the effort to define it in a way that is scientifically accurate and in a way that promotes greater sensitivity to the needs of people described by the term which has been continuous for centuries. The author states that a scientifically sound and socially helpful definition of the term may not be achievable. He opines that it is time to admit that the term mental retardation is, to use Thomas Ssasz's words "scientifically worthless and socially harmful." It is time to face the reality that it is a manifestation of typological reasoning that has created a false and unhelpful categorization of people with very diverse needs and characteristics. Although the implications of abandoning the term for resource allocations and the provision of services must be carefully addressed, the term mental retardation should become an historical artifact of the evolution of the people's thinking about children and adults with developmental disabilities. The millions of people within the spectrum of developmental disabilities who have been described as mentally retarded deserve this change in the manner in which they are regarded and treated.