Health care providers and payers are being asked to weigh data on the economic impact of new interventions along with clinical evidence when making decisions about the care of patients. The notion of incorporating formal health economic assessments into clinical and resource decisions is a difficult concept for many in the health care sector. However, it is the reality in today's environment. To effectively participate in these ongoing discussions, clinicians and other decision makers must be able to understand and critically assess the evidence on economic impact of medical interventions. This second of 2 articles describes the elements of comparative economic evaluations, reviewing the published literature on asthma and rhinitis in an attempt to critically appraise the studies from the perspective of one who might use data for decision making. Unfortunately, the quality of the economic evidence in these two disease states is not extensive. Until better economic analyses are conducted and made available, the allocation of resources for asthma and allergic rhinitis will continue to primarily rely on expert opinion rather than evidence-based literature.