This paper provides an overview of the scientific and practical aspects of assessing health-related quality of life (HRQL). The paper provides a brief overview of developments in the field and then discusses the definition of HRQL. The different types of HRQL measure available to researchers are described, with specific references to urology measures. The paper then focuses on the conceptual and methodological difficulties inherent in patient-centred measures and describes the various means of ensuring scientific soundness in such measures. It concludes that HRQL measures offer much potential to those interested in patient outcomes but that their widespread introduction into research and practice must be carried out with caution.