The Alpha One International Registry (AIR), a multinational research program focused on alpha1-antitrypsin (AAT) deficiency, was formed in response to a World Health Organization recommendation. Each of the nearly 20 participating countries maintains a national registry of patients with AAT deficiency and contributes to an international database located in Malmö, Sweden. This database is designed to increase understanding of AAT deficiency. Additionally, AIR members are engaged in active, wide-ranging investigations to improve the diagnosis, monitoring, and treatment of the disease and meet biennially to exchange views and research findings. The fourth biennial meeting was held in Copenhagen, Denmark, on 2-3 June 2005. This review covers the wide range of AAT deficiency-related topics that were addressed encompassing advances in genetic characterization, risk factor identification, clinical epidemiology, inflammatory and signalling processes, therapeutic advances, and lung imaging techniques.