Objective: Adrenal function in stable asthmatics has been extensively studied. The purpose of this study was to determine the effect of asthma exacerbation on adrenal function. Methods: We studied an observational cohort, convenience sample of patients at a university-affiliated county hospital. Adult patients with asthma who were not steroid-dependent and who presented to the emergency department because of their asthma comprised the study group. All patients were examined and pulmonary function tests were performed. Blood samples for determination of initial cortisol levels were obtained, followed by the administration of .25 mg cosyntropin intramuscularly. Standard therapy with aerosolized albuterol was then initiated. Plasma cortisol levels were measured 30 and 60 minutes later. Steroid therapy was withheld until completion of the rapid cosyntropin stimulation test. Results: A total of 74 patients participated; 64% (47) were women. The range of pretreatment FEV₁ was from 10% predicted to 74% predicted. The range of cortisol levels on presentation was from 1.6 μg/dL to 35.8 μg/dL. Twelve patients had initial cortisol levels greater than 20 μg/dL, a level indicative of physiologic stress. Four patients had initial cortisol levels greater than 30 μg/dL. Mean plasma cortisol levels at 0, 30, and 60 minutes were 13.7 μg/dL (±7.2 μg/dL ), 28.7 μg/dL (±7.4 μg/dL), and 33.0 μg/dL (±8.2 μg/dL). We found an association between evidence of physiologic stress and severe airflow obstruction (P<.03) but no linear correlation (r=–.15). Conclusion: Few patients with asthma have adrenal suppression on presentation. Asthma exacerbation does not provoke a physiologic stressor response in most asthmatic patients. [Cydulka RK, Emerman CL: Adrenal function and physiologic stress during acute asthma exacerbation. Ann Emerg Med May 1998;31:558-561.]