The Agency for Healthcare Research and Quality and the National Institute of Allergy and Infectious Diseases organized a workshop to develop trial concepts that could improve the usage and effectiveness of aeroallergen immunotherapy (AAIT). Expert groups were formed to accomplish the following tasks: 1) Propose a study design to compare effectiveness and safety of subcutaneous versus sublingual AAIT; 2) Propose a study design to compare effectiveness and safety of AAIT using one or a few allergens vs all or most allergens to which a patient is sensitized; 3) Propose a study design to determine whether AAIT can alter the progression of childhood allergic airways disease; 4) Propose a study design to determine the optimal dose and duration of AAIT to achieve maximal effectiveness with acceptable safety. Study designs were presented by the workgroups, extensively discussed at the workshop and revised for this report. The proposed trials would be of long duration, and require large, highly characterized patient populations. Scientific caveats and feasibility matters are discussed. These concepts are intended to help the development of clinical trials that can address some of the major questions related to the practice of AAIT for the management and prevention of allergic airways disease.