The assignment of costs in a cost-effectiveness analysis is a complex and disputed issue. The Panel on Cost-Effectiveness in Health and Medicine was convened to discuss standards that could be applied across a range of areas of cost-effectiveness. Additionally, the Panel had a mandate to resolve some controversial issues about the practice of cost-effectiveness that created difficulty in making comparisons across studies. The Panel proposed these guidelines: (1) Do at least some of the analysis from a social perspective; (2) Assign values to resources that reflect their opportunity costs; (3) Avoid zero counting of resources; (4) Avoid double counting of resources; (5) Make analyses only as exacting as necessary in a study. Difficulties in data collection were discussed. Among other questions considered by the panel were how to assign a value to the patient’s time and which productivity costs to include in a cost-effectiveness analysis. With tools and suggestions from the Panel on Cost-Effectiveness in Health and Medicine, the cost analyst can report costs accurately and provide accurate comparisons of cost performance across states, trial modalities, or diseases.