Primary care physicians commonly see men or women with nocturia (or nocturnal polyuria). Nocturia can have a dramatic impact on a patient' physical and emotional quality of life, including work performance or ability to function, because of the interrupted sleep patterns. It has also been determined that the most important sleep interval is the time from first falling asleep until first awakening. Nocturia is one of the most common and most bothersome symptoms of lower urinary tract symptoms (LUTS). In a man, LUTS is most commonly caused by benign prostatic obstruction (BPO) related to the enlargement of the prostate. In a woman, the most common cause of LUTS is overactive bladder (OAB). This article first explores the different causes and types of nocturia, then describes how to diagnose different types of nocturia (including use of frequency-volume charts), and last, discusses different approaches for managing nocturia (including the use of desmopressin), depending on the type and cause.