This paper examines the issues of deinstitutionalization and mainstreaming from a historical perspective, focusing on the changes over time in views and practices toward retarded individuals and the role of science in the mental retardation field. The parallel development of residential programs and special education programs for individuals with mental retardation is described; and movements toward deinstitutionalization, normalization, and mainstreaming are examined. Excessive concern with the physical settings of services is cited, with the recommendation that the actual social and psychological characteristics within each individual setting be considered. The paper proposes that: (1) services should be matched to each person's needs, regardless of setting which might include the large institutions; (2) such large institutions should train new generations of professionals to work with retarded persons; and (3) large institutions which continue to be used should be humanized. Following the speech is a transcript of a question-and-answer period. It deals with the phenomenon of the decreasing numbers of children labeled as mildly mentally retarded, the state of the existing knowledge base in mental retardation research, and the need for regular education teachers to receive special training before mainstreaming occurs. (JDD)