Bronchodilators are central in the symptomatic treatment of chronic obstructive pulmonary disease (COPD), although there is often limited reversibility of airflow obstruction. Three classes of bronchodilators (β₂-agonists, antimuscarinic agents, methylxanthines) are currently available, which can be used individually, or in combination with each other or inhaled corticosteroids. Novel classes of bronchodilators have proved difficult to develop. The muscarinic β₂-agonist molecules approach likely provides the best opportunity to develop combinations that combine corticosteroids with dual-bronchodilator activities, and thus potentially achieve better efficacy than is apparent with the current combination products that dominate the treatment of COPD.