Bronchial asthma is characterized by episodic airway obstruction and associated with wheezing, a bronchodilator response, an elevation in total serum IgE, and atopy. To determine whether asthma is more common in subjects with severe alpha 1-antitrypsin deficiency (alpha 1-ATD) and airway obstruction, we compared 38 patients who had this condition (Group 1) with 22 control patients with chronic obstructive pulmonary disease (COPD) (Group 2) and with five subjects with alpha 1-ATD and normal spirometry (Group 3). Subjects were evaluated with a symptom questionnaire, pulmonary function testing, intradermal allergen testing, and serum IgE measurement. Self-reported wheezing was a common symptom in all patient groups, but attacks of wheezing with dyspnea were significantly more common in Group 1. Of those patients with airway obstruction, more than 50% showed a bronchodilator response whether suffering from alpha 1-ATD or not. Atopy was more common in Group 1 than in Group 2 (48% versus 27%). Mean serum IgE for all groups was similar but significantly greater in patients with atopy. We estimated the prevalence of asthma in the study groups on the basis of the criteria of attacks of wheezing, reversible airway obstruction, atopy, and that increased IgE. The proportion of patients with asthma in Group 1 was significantly greater than that in Group 2 (22% versus 5%, p < 0.05). Our study shows that with control for the degree of airway obstruction, asthma, as defined, is more common in patients with alpha 1-ATD than in those without it. We suggest that a lack of alpha 1-AT in airways increases the propensity to develop asthma.