Vasopressin (also known as antidiuretic hormone (ADH) or arginine vasopressin (AVP)) has been well described as an important hormone regulating fluid homeostasis and vascular tone. It is synthesised in the supraoptic and paraventricular nuclei of the hypothalamus. Hypothalamic vasopressinergic magnocellular neurons project from the supraoptic nucleus to the posterior pituitary, utilising neurophysins. Vasopressin is then secreted into the circulation for the purpose of osmotic regulation via renal arginine vasopressin 2 (AVP2) receptors which lead to the membrane localization of aquaporin-2 (Aq2) channels in distal renal tubules enhancing water reabsorption from tubular fluid into the circulation. Vasopressin also contributes to vascular tone via arginine vasopressin 1a (AVP1a) receptors. In cirrhotic patients, intestinal bacterial translocation is responsible for overproduction of nitric oxide (NO) via activation of monocytes and lymphocytes and increase in circulating levels of proinflammatory cytokines. These properties make copeptin an interesting surrogate marker of AVP in clinical practice. Copeptin has been shown to be a reliable prognostic marker in decompensated congestive heart failure and a wide variety of other diseases. Limited data are available on its prognostic significance in patients with cirrhosis