Asthma is a heterogeneous clinical syndrome primarily affecting the lower respiratory tract, characterized by episodic or persistent symptoms of wheezing, dyspnea, and cough. The diagnosis of asthma requires these symptoms and demonstration of reversible airway obstruction using spirometry. Identifying clinically important allergen sensitivities is useful. Inhaled short-acting β2-agonists provide rapid relief of acute symptoms, but maintenance with daily inhaled corticosteroids is the standard of care for persistent asthma. Combination therapy, including inhaled corticosteroids and long-acting β2-agonists, is effective in patients for whom inhaled corticosteroids alone are insufficient. The use of inhaled long-acting β2-agonists alone is not appropriate. Other controller approaches include long-acting muscarinic antagonists (eg, tiotropium), and biological agents directed against proteins involved in the pathogenesis of asthma (eg, omalizumab, mepolizumab, reslizumab).