Mediastinal abscess resulting from descending necrotizing mediastinitis is a rare infectious process. Odontogenic infections are the most commonly implicated underlying process. Descending necrotizing mediastinitis is a rapidly progressive infectious process that spreads through the fascial planes of the neck to gain access to the mediastinum. Early recognition of descending necrotizing mediastinitis is important because the reported mortality rate is 30% to 50% even in the antibiotic era. Clues to the diagnosis of descending necrotizing mediastinitis include evidence of severe oropharyngeal infection, neck swelling and crepitations, and complaints of dysphagia and odynophagia. Lateral radiographs of the neck sometimes show gas pockets, but chest films are often negative early in the disease process. A late chest x-ray finding is widening of the superior mediastinum. Therefore, computed tomography (CT) is the imaging procedure of choice. Optimal treatment includes adequate drainage of the neck and mediastinum and broad spectrum intravenous antibiotics. Commonly implicated organisms are alpha-hemolytic streptococci and Bacteroides fragilis.