Over the past 10–15 years, the diagnosis of α1-antitrypsin deficiency (AATD) has markedly improved as a result of increasing awareness and the publication of diagnostic recommendations by the American Thoracic Society (ATS)/European Respiratory Society (ERS). Nevertheless, the condition remains substantially underdiagnosed. Furthermore, when AATD is diagnosed there is a delay before treatment is introduced. This may help explain why AATD is the fourth most common cause of lung transplantation. Clearly we need to do better. The ATS/ERS recommend testing high-risk groups, such as: all chronic obstructive pulmonary disease patients; all nonresponsive asthmatic adults/adolescents; all cases of cryptogenic cirrhosis/liver disease; subjects with granulomatosis with polyangitis; bronchiectasis of unknown aetiology; panniculitis and first-degree relatives of patients with AATD. In terms of laboratory diagnosis, measurement of α1-antitrypsin levels will identify patients with protein deficiency, but cannot differentiate between the various genetic subtypes of AATD. Phenotyping is the current gold standard for detecting rare variants of AATD (except null variants), while advances in molecular diagnostics are making genotyping more effective. An accurate diagnosis facilitates the physician's ability to actively intervene with measures such as smoking cessation and perhaps augmentation therapy, and it will also help provide a better understanding of the natural history of the disease.