OBJECTIVE Previous studies reported that norepinephrine levels increased during acute asthma, while epinephrine levels have remained at normal levels. The purpose of this study was to determine whether the lack of rise in epinephrine levels is due to an inherent defect in catecholamine secretion in asthmatics or is a result of an insufficient stimulus for epinephrine release. METHODS County-owned, university-affiliated emergency department. METHODS Prospective study. METHODS Patients more than 18 years old presenting to the ED with an acute exacerbation of asthma or chronic obstructive pulmonary disease (COPD). METHODS Initial phlebotomy and spirometry were followed by treatment with either albuterol or albuterol and glycopyrrolate. Asthmatic patients received steroids. Phlebotomy and spirometry were performed again after treatment. RESULTS There was no difference in epinephrine levels between patients with asthma and those with COPD either before or after treatment. Norepinephrine levels were higher in patients with COPD, both before and after treatment. There was only a weak correlation between epinephrine levels and pretreatment FEV1 for asthma but not for COPD. CONCLUSIONS Moderate bronchospasm is not a major stimulus for epinephrine release in either acute asthma or COPD.