Objective: This article reviews the process and the considerations on mental retardation terminology change to intellectual disability (ID), and how ID fits within the general construct of disability. Method: Some related sources were reviewed, and the Perspective paper (Schalock et al., 2007) was translated into Persian and added to the article. Results and Conclusion: Increasingly, the term ID is being used instead of mental retardation. The term covers the same population of individuals who were diagnosed previously with mental retardation in number, level, kind, type and duration of the disability and the need of people with this disability for individualized services and supports. This transition has been supported by many organizations. Further discussions are anticipated to be continued in order to refine the construct of ID, improve the reliability of diagnosis, and better understanding on the aspects of human functioning.