Inappropriate intravenous fluid therapy results in increased patient morbidity and mortality. By far the most common fluid and electrolyte problems that confront both chronically and critically ill patients are disturbances in sodium and water balance. Thus, it is important for the infusion therapy nurse to understand the basic pathophysiology of sodium imbalances as well as therapeutic approaches for their correction. Adding to this need is the recognition that, in hospital settings, disorders of sodium and water balance are often iatrogenic.