Methods for the economic evaluation of pharmaceuticals seek to compare therapies in terms of costs and outcomes. Therapeutic benefits and side effects of medicines often impact upon domains of human functioning which can be defined and measured under the general term of health-related quality of life (HRQOL). This paper reviews the rationale behind the use of preference-based HRQOL assessment, such as utility measurement, in economic evaluation studies. It is argued that disease-specific measures and generic health profiles are of limited value for use in economic appraisal studies, particularly where therapies impact upon quality and quantity of life. The conceptual and practical problems arising from the composite outcome measure of quality-adjusted life years (QALYs) are also reviewed.