This report traces the recent recognition given to the needs and feelings of siblings of individuals with mental retardation. The development of social support groups for siblings from 1960 to the present is described, including the establishment of the landmark Brother-Sister Group, the founding of the Association for the Help of Retarded Children's (AHRC) Adult Sibling Support Group, and AHRC conferences on siblings of people with mental retardation and developmental disabilities. Literature written to address the problems of siblings of individuals with mental retardation is reviewed. The impact of several converging factors on sibling concerns is addressed, including the increased longevity of persons with mental retardation, the aging and death of parents who provided care, the closure of institutions, and the return to the community of institutionalized people. The fears and emotional conflicts of siblings of those with mental retardation are identified. Recommendations are made for a future agenda for sibling services that includes having all members of a family involved in future planning, starting services for siblings at an early age, and making genetic information and counseling available to help siblings make decisions about their own parenting. (Contains 15 references.) (CR)