- The elderly are a heterogeneous population group who range from well and completely independent individuals to a smaller proportion who are frail, require help and are high users of the healthcare system. Since health is a state of well-being which includes the domains of social, spiritual, psychological and physical function, each of these domains must be evaluated when we are measuring the health of older adults. In this article, we discuss some of the more important aspects of these domains. If we focus exclusively on the diseases which occur in older adults we will miss important aspects of their health status. We may miss the interactions of several different disease processes occurring in 1 individual, and the impact of those diseases on the individual's ability to live independently and his or her quality of life. In this article, we not only justify the measurement of function, cognition, affect and quality of life in the elderly but we also describe the necessary measurement qualities of instruments used to measure health-related quality of life in the elderly. We provide some examples of measurement approaches with which we as researchers and health workers are familiar.