Mediastinitis occurring from a descending odontogenic infection occurs rarely. The diagnosis is sometimes difficult to make and is often delayed until the patient is in extremis. The physical examination is often nondiagnostic, but may include brawny edema of the neck and chest. CT scanning provides the most accurate diagnostic information. The treatment is always surgical, in combination with appropriate antibiotics. Five patients with mediastinitis secondary to odontogenic infections are presented, and the technique of transcervical drainage of the anterior and posterior mediastinum is reviewed.