This chapter discusses the diagnosis, evaluation and management of hypertensive emergencies. It describes special considerations for aortic dissection, acute ischemic stroke, acute intracerebral hemorrhage (ICH), and preeclampsia and eclampsia. The critical management of hypertensive emergencies depends on the presence of end-organ damage. Only patients with a diagnosis of hypertensive emergency require immediate interventions in the emergency department for lowering blood pressure. Patients with chronically elevated blood pressure may suffer detrimental consequences if their blood pressure is lowered too quickly. Dramatic and rapid decreases in blood pressure can result in critical hypoperfusion of the brain, heart, and kidneys, resulting in ischemia or infarction. Patients with hypertensive urgency can be managed as outpatients as long as reliable follow-up can be arranged. They are usually started on oral antihypertensives with a goal of lowering their blood pressure to less than 160/100 mmHg over 12-48 hours.