Health outcomes research (HOR) is an important source of knowledge regarding the effectiveness of health care treatments and interventions which focus on providing benefits in terms of those results which are important for patients. Medical research has traditionally focussed on the measurement of clinical variables, such as symptoms or laboratory tests, as a means of determining the results of medical interventions. Although HOR uses such tests, it also places great emphasis on the use of other measures such as health-related quality of life, satisfaction with treatment, and cost-effectiveness. The results obtained should be incorporated in the evaluative process and in disease management to determine the effectiveness of health care services in improving the population's health.