"Mentally retarded cases: have a difference between their retarded intelligence and their real age physical abilities.Interior design should deal with this issue :their real needs as children according to the level of intelligence ,and their body dimensions. Particular considerations for children are those related to safety and comfort in designing interior architectural elements and; furnishing; such as stairways, ramps; railings on stairs, balconies, floors, bathrooms, doors, windows, walls, and ceilings. Caring for Mentally Retarded: in Egypt, it has its roots in Pharaonic, Coptic, and Islamic times. Medical texts produced by scholars at the school of Medicine in Alexandria are still preserved today .Medical writers (from the medieval times ),such as AL-Razi , AL-Majusi,Ishaq Ibn Imran and ,Ibn Sina,were among many who borrowed from Galen ( Alexandria,2nd Cent.AC),and other ancient authors, who broadened the scope to include a more thorough investigation into mental disability and illness (Lababidi 2002).The first Islamic hospital incorporated wards for the insane, and was built in Fostat( Old Cairo) in 872 by Ahmed Ibn Tulun However, the best known was built in 1284 by AL-Mansur Qalawun.Such hospitals were called "maristan(s)" . From The eighth until the fifteenth centuries, AL-Azhar University took lead in teaching the disabled. Modern Egyptian achievements: Social welfare endowments "the Wakfs" during the reign of Mohamed Ali and Khedive Ismail in the nineteenth century made possible the expansion of hospitals for the mentally retarded , but they were used as a last resort ;the family was considered , by the society, to be the first responsible of taking care of her disabled child . Beginning of the twentieth century,charitable societies focused on helping the deprived and the disabled.In 1940,the Egyptian Ministry of Education directed its attention to educating the mentally retaded.In 1953,the Ministry of Social Affairs stipulated the Social Security Law (No.116) under which the disabled and handicapped could find services that would help to prepare them for suitable jobs. In the1990's, the NGO community in Egypt has played an important role in its advocacy for the protection and development of children.The research aims were: To identify the structural relations between socio-psychological factors related to the interior design, meaning and use of housing for the mentally retarded for children and youth (age6-18years) The methodology required: POE of eight care centers, four cases are from private sector, and four cases are from the government sector. They are newly designed to accommodate the mentally retarded. The selection was based on social levels, and available facilities, in term of interior design determinates such as: the adequacy of spaces in relation to the activity it is designed for, the appropriateness of furnishing , furniture arrangement and type of furniture used in each space , the fulfillment of design considerations set in the standards for mental health facilities.Procedures and instruments: of data gothering were based on direct observation notes on the actual state of the interior spaces and furniture , sketches of furniture layout and photographs. Interviews conducted randomly on the working staff were about: Age groups and number of inmates accepted in the facility. Types of mental disability dealt with Care services provided in the facility. Working and daily schedule. Activities performed in each space; individually? By groups? Involvement of parents in some activities? Which ones? How? Special design, equipment or feature used for a specific function related to the mentally retarded? Maximum number of persons/ room? The caring mother's bedroom in relation to inmates. The survey covered each zone in the building ( the entrance, reception area, classes, work shops living area, speech therapy clinics, gymnasium, kitchen, restaurant, corridors, court yard cafeterias, bathrooms, and multi purpose areas); according to its furnishing, and the finishing of its elements. Results were compared with the standards of designing for mentally disabled people, to reach design guidelines for property functioning care centers."