Objective　To investigate the incidence， clinical characters and pathogenesis of hyponatremia following acute stroke in the elderly patients.Methods　The clinical,serum natrium and CT data of 41 cases with hyponatremia following acute stroke in the elderly patients were retrospectively analysed.Results The incidence of hyponatremia following acute stroke in the elderly patients was 16.02% (taking hemorrhagic stroke),the occurrence of the patients' coma induced by hyponatremia and the fatality rate were higher than the controls (P＜0.05);Hyponatremia correlated closely with the localization of lesions in CT, the focus in brain ganglion (induding thalamus) and hematocele in the ventricles of brain caused easily hyponatremia.Conclusion　Dysfunction of hypothalamus-pituitarium was one of the risk factors in causing hyponatremia following acute stoke in the elderly patients.