Asthma is a common chronic disorder, with a prevalence of 8 to 10 percent in the U.S. population. From 5 to 10 percent of patients have severe disease that does not respond to typical therapeutic interventions. To prevent life-threatening sequelae, it is important to identify patients with severe asthma who will require aggressive management of exacerbations. Objective monitoring of pulmonary status using a peak flow meter is essential in patients with persistent asthma. Patients who have a history of fragmented health care, intubation, or hospitalization for asthma and those with mental illness or psychosocial stressors are at increased risk for severe asthma. Oxygen, beta2 agonists, and systemic corticosteroids are the mainstays of acute asthma therapy. Inhaled anticholinergic medications provide additional bronchodilation. In patients who deteriorate despite usual therapeutic efforts, evidence supports individualized use of parenteral beta2 agonists, magnesium sulfate, aminophylline, leukotriene inhibitors, or positive pressure mask ventilation before intubation.