Alpha-1 antitrypsin deficiency (AATD) is associated with an increased risk of pulmonary emphysema and liver disease. The growing interest in this deficiency in Spain led to the development of the Spanish Registry of Patients with Alpha-1 Antitrypsin Deficiency (REDAAT) in 1993. At present, the REDAAT is a network of more than 350 health care professionals and the database includes a total of 511 individuals. The adult population included consists of 469 individuals (91.8% of the total) and their phenotype distribution is: 348 Pi*ZZ (74.2%), 100 Pi*SZ (21.3%) and 21 carriers of rare variants (4.5%). The most frequent diagnosis is lung disease (74.6%). Patients with chronic obstructive pulmonary disease (COPD) registered in the REDAAT constitute approximately 15% of the expected cases of AATD-related COPD in Spain. Pi*ZZ showed more severe impairment in lung function and younger age at baseline compared with Pi*SZ. The mean decline in FEV1 in the Pi*ZZ subgroup was -23 ml/year (SD:142.8), being -18 ml/year (SD:108.8) in Pi*SZ. Forty-five percent of the Pi*ZZ individuals received augmentation therapy. A total of 61 deaths was recorded. The characteristics of the REDAAT population demonstrate some differential trends compared to other series: distribution of phenotypes, inclusion of children and patients treated with replacement therapy. Patients with the Pi*SZ phenotype were older and had milder lung function impairment. The most important challenge of this registry is to collect good quality long-term data that will allow better understanding of the natural history of the disease in real life.