Nocturia is a common symptom in the elderly, which profoundly influences general health and quality of life. One consequence of nocturia is sleep deterioration, with increased daytime sleepiness and loss of energy and activity. Accidents, e.g., fall injuries, are increased both at night and in the daytime in elderly persons with nocturia. Nocturia is caused by nocturnal polyuria, a reduced bladder capacity, or a combination of the two. Nocturnal polyuria can be caused by numerous diseases, such as diabetes insipidus, diabetes mellitus, congestive heart failure, and sleep apnoea. In the nocturnal polyuria syndrome (NPS), the 24-h diuresis is normal or only slightly increased, while there is a shift in diuresis from daytime to night. NPS is caused by a disturbance of the vasopressin system, with a lack of nocturnal increase in plasma vasopressin or, in some cases, no detectable levels of the hormone at any time of the 24-h period. The calculated prevalence of NPS is about 3% in an elderly population, with no gender difference. In NPS, there are serious sleep disturbances, partly due to the need to get up for micturition, but there is also increased difficulty in falling asleep after nocturnal awakenings and increased sleepiness in the morning. The treatment of NPS may include avoidance of excessive fluid intake, use of diuretics medication in the afternoon rather than the morning, and desmopressin orally at bedtime.