Hyponatremia is a very common electrolyte disorder and is a significant independent predictor of medical prognosis and costs. Tolvaptan is a vasopressin receptor antagonist developed for the treatment of hyponatremia. It has its principal application in the treatment of euvolemic and hypervolemic hyponatremia. Its major role is in the treatment of heart failure (HF), cirrhosis and the syndrome of inappropriate antidiuretic hormone secretion (SIADH). While at present tolvaptan has not demonstrated long term survival benefit with its use, it clearly has proven short term efficacy in the management of hyponatremia by demonstrating improvement in serum sodium levels at an acceptable rate without evidence of over-correction.