Over the last decade, there has been an explosion of interest in issues related to quality of life (QoL). While QoL for persons with mental retardation has long been an interest, and there is a foundation for the assessment of QoL for this population, there is still much to be done. This article describes QoL assessment for persons with mental retardation, including the purpose of such assessment. Quality of life is defined as multiple measures of physical, material, social, emotional, and productive well-being. Ways to measure quality of life and how to fit QoL measurement into the broader context of assessment are also discussed.