To identify major problems that obscure understanding of quality of life; to differentiate quality of life from other closely related concepts, and to offer a definition of quality of life. Quality of life is a term frequently used, but seldom defined, in nursing research. Multiple interpretations and measures make evaluating research difficult. The need to clarify concepts, develop nursing theory, and enhance communication is significant. Concept clarification is also essential for research instrument development and evaluation. ORGANIZING CONSTRUCT AND SCOPE: Concept analysis as proposed by Walker and Avant. Preconceived theories were avoided to keep the analysis as unbiased as possible. The analyst considered many descriptions of quality of life, but eventually included only those in the scientific literature. CINAHL, Medline, Psych-Info, ERIC, Social Science Abstracts, and reference lists from published articles in nursing, medicine, psychology, and sociology were used. Twenty-seven theory-based articles and book chapters published since 1989 and a convenience sample of 88 research articles published in 1997 were used. This sample was selected from 16,480 articles published 1993 to 1998. Concept clarification comparisons to identify the major attributes of several closely related concepts, including well-being, satisfaction with life, and functional status. Major attributes were validated by a panel of cohorts who met weekly for five consecutive weeks for the purpose of analyzing various concepts. Quality of life is comprised of subjective indicators such as well-being and satisfaction with life and objective indicators, such as functional status. Continued dialog and research is necessary to distinguish between the concepts of health and quality of life. A model showing the relationships among quality of life, well-being, functional status, and satisfaction with life is provided and a definition of quality of life is offered. Researchers and authors should include the definition of quality of life used in their work. Instruments should reflect the theoretic definition used. Care should be taken to clarify if functional status, well-being, satisfaction with life are the concepts under consideration as reflecting a part of overall quality of life.