The 15D is a generic, comprehensive, 15-dimensional, standardized, self-administered measure of health-related quality of life (HRQoL) that can be used both as a profile and single index score measure. This paper examines the acceptability, reliability, validity, discriminatory power and responsiveness to change of its health state descriptive system and valuation system and presents some examples of applications. As a profile measure on roughly comparable dimensions the 15D performs equally well as the Nottingham Health Profile (NHP) and SF-20, in some respects even better, and clearly better than EQ-5D. The remaining nine to ten dimensions of the 15D provide a large reserve in terms of discriminatory power and responsiveness to change. The valuation system is based on an application of the multiattribute utility theory. The single index score (15D score) on a 0-1 scale, representing the overall HRQoL, is calculated from the health state descriptive system by using a set of population-based preference or utility weights. The 15D scores are shown to be highly reliable, sensitive and responsive to change, generalisable at least in Western-type societies, and particularly valid for deriving quality-adjusted life years (QALYs) gained for resource allocation purposes. The instrument is recommended by the Washington Panel and is available in several languages for clinical economic evaluation and population studies.