OBJECTIVE To describe issues to be considered when measuring the quality of life (QOL) of patients with cancer. METHODS Published articles and books, conference proceedings, and abstracts. RESULTS A review of the existing literature reveals an emerging field of research and considerable discussion of measurement issues. Consensus is growing about measurement approaches to this subjective concept; however, agreement differs regarding specific aspects of measurement approaches and interpretation of data. CONCLUSIONS The purpose of the QOL assessment and how the data will be analyzed are the main determinants of the choice of assessment and measurement approaches. Differences regarding how QOL is measured may be encountered based on a clinical or research purpose. CONCLUSIONS QOL assessments may be used as part of data collection to address a specific research question or may be used to guide clinical practice. Research findings used to guide clinical practice should be evaluated for validity, reliability, and fit of the sample before being incorporated into clinical practice. QOL assessment in clinical practice may be used as an exploratory tool to identify potential problems or may be used to evaluate the effectiveness of a targeted intervention.