Background and Aim: Shifting paradigms about how to assess the support needs of person with intellectual disability, in 1980, posed necessity of design and development of appropriate tools more than ever. In this regard, American Association on intellectual and developmental disabilities developed the supports Intensity scale to respond the lack of an appropriate tool. The aim of this study was to do the cultural adaptation and evaluation of psychometric properties of supports intensity scale in adult people with intellectual disability.

Materials and Methods: In this descriptive – analytic study, 43 adult persons with intellectual disability participated. Translation and adaptation of the SIS through International Quality of Life Assessment (IQOLA ) protocol was done. Validity of the test was evaluated by qualitative content validity. Internal consistency and test-retest reliability were used for evaluation of reliability.

Results: Based on the IQOLA protocol, The SIS had easy translation and relatively good quality. According to results, all items of the test had content validity. Cronbach's alpha coefficients fall in the range (.80-.99) and ICC ranged from .90 to .99

Conclusion: The results of this study showed that the Persian version of the SIS has good validity and reliability for identifying pattern and intensity of needed supports in adult people with intellectual disability.

Key words: Adaptation, Validity, Reliability, Intellectual disability, Supports Intensity Scale