Cost-effectiveness analyses are routinely performed to determine whether the additional cost of a novel therapy is balanced by additional effectiveness. The definitions of costs and effects involve a variety of assumptions, both in general economic terms and with regard to the specific medical setting under consideration. Similarly, differing criteria for acceptability of cost-effectiveness estimates can be used to generate different conclusions regarding cost-effectiveness. The issues and problems inherent in economic evaluation are discussed by an analysis of findings with the platelet glycoprotein IIb/IIIa inhibitor abciximab in the EPIC (Evaluation of 7E3 for the Prevention of Ischemic Complications) study in high-risk patients undergoing percutaneous transluminal coronary angioplasty.