All medical interventions carry costs, and the economic implications are a major consideration when any change in medical practice is proposed. New drugs are often more expensive than those that they are designed to replace, and the introduction of new procedures may also entail increased costs. Medical costs include not only the cost of the drug itself, but also the induced costs (or sometimes, cost savings) such as the costs of administering the drug and the consequent levels of use of other medical resources, including medical personnel. The ESSENCE study (Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-wave Coronary Events)—a double blind, randomised trial of the low molecular weight heparin enoxaparin and unfractionated heparin (UFH) in unstable angina and non-Q wave myocardial infarction1—addressed this issue by means of a prospectively designed economic study to evaluate the cost implications in the light of clinical outcomes.2The ESSENCE economic study was undertaken on those patients in the US, and examined both the use of medical resources and the medical costs to 30 days.