Severe hypertension is a frequent condition among patients presenting to emergency departments. Historically, this has been referred to as a hypertensive crisis. In addition, these hypertensive crises have been further divided into either hypertensive emergencies or urgencies depending on the presence or absence of target organ damage, respectively. The management differs between these crises in both the rapidity of blood pressure correction and the medications used. Hypertensive emergencies must be treated immediately with intravenous antihypertensive medications. However, hypertensive urgencies may be treated with oral antihypertensive agents to reduce the blood pressure to baseline or normal over a period of 24–48 hr. Appropriate identification, evaluation, and treatment of these conditions are of great importance in the emergency department to prevent progression of organ damage and death. The purpose of this article is to provide an overview of the hypertensive crises and their management.