The definition of nocturia is a critical factor in evaluating its epidemiology. The International Continence Society (ICS) classifies nocturia as one of the urinary storage symptoms and defines nocturia as “the complaint that the individual has to wake at night one or more times to void…each void is preceded and followed by sleep.” Several other definitions with subtle differences have also been published. Nocturia is extremely common among older adults, with incidence and prevalence increasing with advancing age. The cause is generally considered multifactorial, but a number of common clinical conditions seen in older adults increase risk. This chapter reviews the epidemiology, evaluation and treatment for nocturia in geriatric patients.