Nocturia, i.e. nocturnal voiding episodes, is a symptom which can occur at all ages, but there is an age-related increase in both men and women. Both health and quality of life are deteriorated by nocturia. Sleep is disturbed, with daytime sleepiness and reduced well-being as consequences. The risk of fall injuries is increased among elderly persons who need to get up several times at night for toilet visits. Nocturia is associated with an increase in nocturnal urine output, and an increased number of nocturnal voids indicates a shift of urine output from the daytime to the night. One of the aims of the treatment of nocturia is therefore to normalise the circadian rhythm of diuresis.