Our broad objective is to promote reasoned priority setting in asthma care. Over the last four years, we have developed the Asthma Policy Model, a mathematical simulation of the clinical management of asthma. We have used this model to estimate health and economic outcomes and to evaluate the cost-effectiveness of different strategies for managing the disease. To our knowledge, the Asthma Policy Model represents the state of the art in asthma-related pharmacoeconomic evaluation. We now request three years of funding to refine the model, to apply it to understudied yet highly vulnerable patient populations, and to address new clinical and resource allocation decisions. Our first Specific Aim is to expand the Asthma Policy Model, improving its focus on children and underserved patient populations and broadening its capacity to simulate the impact of treatment: we will enlarge the definition of patient sub-populations; we will consider new pharmacologic and non-pharmacologic interventions; we will refine the model's measures of intervention efficacy and side-effects; and we will conduct exploratory, "what-if" evaluations of interventions to improve adherence to therapy. Our second Specific Aim is to perform a series of model-based policy evaluations: (1) What are the clinical and economic costs of non- adherence to the 1997 NIH Guidelines for the Diagnosis and Management of Asthma in the United States? (2) Would a comprehensive program of asthma pharmacotherapy and disease management for patients in underserved populations be cost-effective? Could it simultaneously improve clinical outcomes, avoid unnecessary resource consumption, and reduce overall costs? Given the historical lack of success in promoting adherence to therapy in these populations, how sensitive are results to compliance rates? (3) What impact do toxicity-related, quality-of-life concerns have on patient outcomes, economic costs, and the cost-effectiveness of inhaled corticosteroid therapy in asthma? This research assembles experts in asthma epidemiology and pharmacotherapy (Drs. Weiss, Fuhlbrigge, Kitch, and Moy), environmental exposure assessment (Dr. Leaderer), burden of disease in urban, minority populations (Dr. Cloutier), biostatistical analysis (Dr. Kuntz), and simulation modeling and economic evaluation (Dr. Paltiel) to explore cost-effective solutions to the asthma epidemic.