Although acute pericarditis is most often associated with viral infection, it may also be caused by many diseases, drugs, invasive cardiothoracic procedures, and chest trauma. Diagnosing acute pericarditis is often a process of exclusion. A history of abrupt-onset chest pain, the presence of a pericardial friction rub, and changes on electrocardiography suggest acute pericarditis, as do PR-segment depression and upwardly concave ST-segment elevation. Although highly specific for pericarditis, the pericardial friction rub is often absent or transient. Auscultation during end expiration with the patient sitting up and leaning forward increases the likelihood of observing this physical finding. Echocardiography is recommended for most patients to confirm the diagnosis and to exclude tamponade. Outpatient management of select patients with acute pericarditis is an option. Complications may include pericardial effusion with tamponade, recurrence, and chronic constrictive pericarditis. Use of colchicine as an adjunct to conventional nonsteroidal anti-inflammatory drug therapy for acute viral pericarditis may hasten symptom resolution and reduce recurrences.