Hypertension affects an estimated thirty percent of all Americans, a number expected to climb as the population ages. At some point in their life, approximately one percent of these patients will experience a hypertensive crisis-either a hypertensive urgency or emergency. These rapid and worrisome elevations in blood pressure account for many visits to emergency departments and urgent treatment in primary care settings. Patients with hypertensive crises may be asymptomatic, or may present with encephalopathy, chest pain, heart failure, headache, epistaxis, and a number of other clinical disorders. The approach to treating these patients varies widely throughout the world, primarily because of the lack of quality clinical trial data that guides the treatment of this fairly large population of patients with hypertensive crises. In this paper, the categorization of hypertensive urgencies and emergencies will be reviewed. While the majority of the patients have longstanding primary hypertension with sometimes erratic and inadequate treatment, the hypertensive crisis may also be an indicator of another underlying clinical process. The pathophysiology and epidemiology of these conditions will be discussed. The current guidelines for treatment will be summarized. Additionally, the use and indications for various parenteral and intravenous drugs will be described.