Nocturnal waking in urination (nocturia) is a common feature in patients with multiple system atrophy (MSA). Degeneration of arginine vasopressin (AVP) neurons in the suprachiasmatic nucleus in this disorder may lead to nocturnal polyuria, which has been treated with intramuscular desmopressin. We also prescribed 5 microg of intranasal desmopressin once a night in 3 MSA patients, who had nocturnal polyuria with abnormal circadian rhythm of the plasma AVP. During the treatment, all patients showed an improvement in their nocturia without serious adverse effects.