Novel biologic agents have allowed clinicians to achieve improved patient outcomes. Appropriate pharmacoeconomic analyses demand evaluation of all relevant costs, including the treatments, the disease and comorbidities, and costs of alternative treatments, including their short- and long-term side effects. Only with complete data can the value of therapies be correctly estimated. By assessing costs, pharmacoeconomic studies complement studies of efficacy and safety, helping to determine the relationships of treatment and outcome. This article provides a broad framework for understanding and evaluating published economic analyses and identifying the key costs and benefits caring for patients with asthma and other immune diseases.