Alpha1-antitrypsin (AAT) deficiency was first described in 1963 together with its associations with severe early-onset basal panacinar emphysema. The genetic defects leading to deficiency have been elucidated and the pathophysiologic processes, clinical variation in phenotype, and the role of genetic modifiers have been recognized. Strategies to increase plasma (and hence tissue) concentrations of AAT have been developed. The only recognized specific therapeutic strategy is regular infusions of the purified plasma protein, and evidence confirms its efficacy in protecting the lung (at least partially). Early detection and modification of lifestyle remains crucial to the management of AAT deficiency.