The profound developmental disability (DD) means the most severe disability. However, there is no exact definition yet in korea. I reviewed the concept of DD and the meaning of the profound disability through the laws and policies of the United States and Korea, as well as the medical perspective (Ex: ICD, DSM) and the social model perspective (Ex: ICF). The concept of DD varies depending on the size and type of budget support and policy. Therefore, when establishing eligibility for DD services, the definitions of DD impacts on policy. The developmental disabilities (DDs) means a group of conditions due to an impairment in only adaptive function and comprehensive concept. if more stringent criteria applied, DD coexisting with intellectual disability is considered a severe DD. Severe and profound intellectual deficits shows a high correlation with strong impairments in adaptive behavior. This condition can be classified as the most severe DD or profound DD. Also, adding information on risk of harm to self or others and community resources in profound DD will be become a complementary concept.