This article provides an overview of the 2002 American Association on Mental Retardation's (AAMR's) "Definition, Classification, and Systems of Supports" (the 2002 System) and discusses its relationship to salient international trends and several scientific and judgmental issues currently impacting the field of intellectual disabilities (ID). Five significant international trends--ecologic perspective, disablement as a limitation in functioning, multidimensionality of ID, linking assessment to intervention, and the importance of clinical judgment--are identified and related to the 2002 System. The scientific and policy issues which impact definitional, classification, and intervention systems include: distinguishing among naming, defining, and classifying; answering the question, "what is a disability?"; delineating the essential characteristics of the condition; determining the relationship between intelligence and adaptive behavior; and defining the class. The 2002 System is critiqued and discussed within the contemporary context of thinking about and supporting people with ID. The authors conclude that time will tell how effective the 2002 AAMR System is in meeting the challenge of defining the framework of ID and providing a universally applicable and effective model for the diagnosis, classification, and planning of supports for persons with ID.