Outcomes research is a broad umbrella term without a consistent definition. However it tends to describe research that is concerned with the effectiveness of public-health interventions and health services; that is, the outcomes of these services. Attention is frequently focused on the affected individual - with measures such as quality of life and preferences - but outcomes research may also refer to effectiveness of health-care delivery, with measures such as cost-effectiveness, health status and disease burden. The present review details the historical background of outcomes research to reveal the origins of its diversity. The value and relevance of outcomes research, commonly employed research techniques and examples of recent publications in the area are also discussed.