Background: The importance of the valid assessment of quality of life (QOL) is heightened with the increased use of the QOL construct as a basis for policies and practices in the field of intellectual disability (ID). Method: This article discusses the principles that should guide the measurement process, the major interrogatories (i.e. who, what, when, where, why, and how) of QOL measurement, issues and procedures in the cross-cultural measurement of QOL, and the current uses of QOL data. Results: Based on the above methods, the article presents a number of important guidelines regarding QOL measurement. Conclusion: From a measurement perspective the use of the QOL construct is changing. Initially it was used as a sensitizing notion, social construct, and unifying theme. Increasingly, it is being used as conceptual framework for assessing quality outcomes, a social construct that guides quality enhancement strategies, and a criterion for assessing the effectiveness of those strategies. This new role places additional emphasis on the valid assessment of one's QOL.