Purulent pericarditis represents a subset of pericardial disease usually due to a nonviral infectious agent. The presentation is often acute, with rapid progression to tamponade unless a drainage procedure is performed. Although several infectious agents account for the majority of infections, the differential diagnosis is broad. Often, patients with more exotic infectious causes have risk factors for these agents that can be identified by careful history-taking. Distinguishing a bacteremic source from infection acquired by contiguous spread is particularly important. Although most infections spread contiguously are a complication of recent surgery or nearby pneumonia and are, therefore, apparent to the physician, others may be less obvious. For example, head and neck space infections may track to the retropharyngeal space and, from there, posteriorly to the so-called "danger" space, which connects inferiorly to the mediastinum and the pericardium. Failing to identify this source of tracking infection may lead to inadequate drainage as well as inappropriate empiric antibiotic therapy. In acute cases, needle drainage with appropriate staining and culturing of the fluid is adequate for diagnosis and initial management of the complications of fluid collection in the closed space of the pericardial sac. Pericardial biopsy may be the sole method of identifying an etiologic agent, particularly in chronic cases in which granulomatous disease is more commonly seen. In select cases, pericardial window or pericardiectomy procedures are needed to limit complications of reaccumulation of fluid.