Virtually all investigators now agree that self-induced water intoxication, symptomatic hospital-acquired hyponatremia, and hyponatremia associated with intracranial pathology are true emergencies that demand prompt and definitive intervention with hypertonic saline. A 4- to 6-mmol/L increase in serum sodium concentration is adequate in the most seriously ill patients and this is best achieved with bolus infusions of 3% saline. Virtually all investigators now agree that overcorrection of hyponatremia (which we define as 10 mmol/L in 24 hours, 18 mmol/L in 48 hours, and 20 mmol/L in 72 hours) risks iatrogenic brain damage. Appropriate therapy should keep the patient safe from serious complications of hyponatremia while staying well clear of correction rates that risk iatrogenic injury. Accordingly, we suggest therapeutic goals of 6 to 8 mmol/L in 24 hours, 12 to 14 mmol/L in 48 hours, and 14 to 16 mmol/L in 72 hours. Inadvertent overcorrection owing to a water diuresis may complicate any form of therapy, including the newly available vasopressin antagonists. Frequent monitoring of the serum sodium concentration and urine output are mandatory. Administration of desmopressin to terminate an unwanted water diuresis is an effective strategy to avoid or reverse overcorrection.