The association of severe hyponatremia and the ingestion of large quantities of beer, termed beer potomania, has been known for several years. We report two new cases, and review 20 others from the medical literature. These patients usually have a history of binge beer drinking, poor dietary intake, and then present with severe hyponatremia and various mental status changes or seizures. Typical laboratory findings include hyponatremia, hypokalemia, and a very dilute urine. The patients respond quickly to the administration of sodium chloride containing i.v. fluids. We propose that the pivotal pathophysiologic mechanism in beer potomania syndrome is the minimal intake of solute and the hypoosmolality of the beer ingested. This will lead to the inability to excrete sufficient amounts of free water to keep up with the ingestion of large quantities of the hyposmolar beer. Treatment with isotonic sodium chloride results in the rapid clearance of the accumulated excess free water.