Patients with severe infections of the potential spaces of the head and neck are commonly managed in the ICU. These infections may present with devastating complications such as airway obstruction, jugular septic thrombophlebitis, lung abscess, upper airway abscess rupture with asphyxiation, mediastinitis, pericarditis, and septic shock. A thorough understanding of the anatomy and microbiology of these infections is essential for proper management of these patients. Retropharyngeal, danger, prevertebral, lateral pharyngeal, and submandibular space infections and their site-specific clinical manifestations, complications, and therapeutic interventions are discussed.