Chronic obstructive pulmonary disease (COPD) exacerbations are important events that contribute to worsening health status, disease progression, and mortality. They are mainly triggered by respiratory viruses (especially rhinovirus, the cause of the common cold), but airway bacteria are also involved in their pathogenesis. Exacerbations are associated with both airway and systemic inflammation and, this is mainly neutrophilic in origin. Some patients are especially prone to develop exacerbations, and these have been identified as a high-risk group with increased airway inflammation and greater disease progression. Management of acute exacerbations involves therapy with oral corticosteroids and/or antibiotics, and new therapies are needed. A number of interventions may prevent exacerbations, including vaccination, long-acting bronchodilators, antiinflammatory agents, and long-term antibiotic therapy. Understanding of the pathophysiological mechanisms of COPD exacerbations is important to develop novel therapies.