Environmental exposures have been recognized as critical in the initiation and exacerbation of asthma, one of the most common chronic childhood diseases. The National Institute of Allergy and Infectious Diseases (NIAID), National Institute of Environmental Health Sciences (NIEHS), National Heart, Lung, and Blood Institute (NHLBI), and Merck Childhood Asthma Network (MCAN) sponsored a joint workshop to discuss the current state of the science with respect to the indoor environment and its effects on the development and morbidity of childhood asthma. The workshop included U.S. and international experts with backgrounds in allergy/allergens, immunology, asthma, environmental health, environmental exposures and pollutants, epidemiology, public health, and bioinformatics. Workshop participants provided new insights into the biologic properties of indoor exposures, indoor exposure assessment and exposure reduction techniques. This informed a primary focus of the workshop-- to critically review trials and research relevant to the prevention or control of asthma through environmental intervention. The participants identified important limitations and gaps in the scientific methodologies and knowledge, and proposed and prioritized areas for future research. The group reviewed socioeconomic and structural challenges to changing environmental exposure and offered recommendations for creative study design to overcome these challenges in trials to improve asthma management. The recommendations of this workshop can serve as guidance for future research in the study of the indoor environment and on environmental interventions as they pertain to the prevention and management of asthma and airway allergies.