Vasopressin and its analogue, terlipressin, are potent vasopressors that may be useful therapeutic agents in the treatment of cardiac arrest, septic and catecholamine-resistant shock and oesophageal variceal haemorrhage. The aim of this article is to review the physiology and pharmacology of vasopressin and summarise its efficacy and safety in clinical trials and its subsequent therapeutic use. Recent studies indicate that the use of vasopressin during cardiopulmonary resuscitation may improve the survival of patients with asystolic cardiac arrest. Vasopressin deficiency can contribute to refractory shock states associated with sepsis, cardiogenic shock and cardiac arrest. Low doses of vasopressin and terlipressin can restore vasomotor tone in conditions that are resistant to catecholamines, with preservation of renal blood flow and urine output. They are also useful in reducing bleeding and mortality associated with oesophageal variceal haemorrhage. The long-term outcome of the use of these drugs is not known.