Stroke is the third largest cause of death, after heart disease and cancer. Stroke usually leaves severe mental and physical sequels for patient. It creates a financial burden on patient's family and society. Hyponatremia accentuates disease status and often is overlooked. Thus, the author did a research of this subject with the aim of: Review on clinical and subclinical characteristics, result and treatment process development of Hyponatremia of a stroke patient. By studying 30 patients, the authors see that Hyponatremia is able to happen from first 24 hours to 21st day after the onset of brain damage. First 24 hour Hyponatremia patient often has a very severe clinical symptom. Clinical symptom of Hyponatremia patient is difficult to detect especially coma patient and Mechanically Ventilated Patient. The most common symptom is mental disorder. Rehydration therapy is not really reasonable.