BACKGROUND--Previous estimates of the survival times of patients with alpha 1-antitrypsin deficiency have been based on selected patients. METHODS--The survival times of 397 patients with severe alpha 1-antitrypsin deficiency identified by pulmonary impairment (index cases) or through family studies (non-index cases) were compared. RESULTS--The overall median survival time was 54.5 years with no significant difference between men and women. Survival for index cases was less than for the non-index cases regardless of smoking history (49.4 years and 69.3 years respectively). When index and non-index cases were analysed separately there was no difference between the survival of smokers and never smokers in the index group. In the non-index group smokers had a shorter survival time than never smokers. The survival time of never smokers was similar to that of the normal Danish population. CONCLUSIONS--The prognosis of severe alpha 1-antitrypsin deficiency is better than previously assumed and, although smoking is a major risk factor, the development of emphysema in patients with severe alpha 1-antitrypsin deficiency is multifactorial.