Nocturia is a common condition in the elderly that profoundly influences general health and quality of life. It appears to predict a higher risk of death. One consequence of nocturia is sleep deterioration, with increased daytime sleepiness and loss of energy and activity. Accidents, e.g. falls, are increased both at night and during the day in elderly persons with nocturia. Nocturia is caused by nocturnal polyuria, reduced voided volumes, or a combination of the two. Nocturnal polyuria can be caused by numerous diseases, e.g. diabetes insipidus, diabetes mellitus, congestive heart failure, and sleep apnoea. A disorder of the vasopressin system, with very low or undetectable vasopressin levels at night, is manifested as an increased nocturnal urine output, which in the most extreme cases reaches 85% of the 24-h diuresis: the prevalence of low or undetectable vasopressin levels at night has been estimated to be 3-4% in those aged >or= 65 years. Treatment of nocturia may include avoiding excessive fluid intake and use of diuretic medication in the afternoon rather than the morning, oral desmopressin at bedtime in cases of nocturnal polyuria, and antimuscarinic agents in the case of overactive bladder or impaired storage capacity of the bladder.