Objectives: The aim of work is to study nocturia with its different causes with special consideration for nocturnal polyuria in elderly male patients suffering from nocturia, and to investigate the safety and effectiveness of oral desmopressin therapy in the treatment of such patients.Materials and Methods: This study was conducted on 30 male patients aged 63 ±2.7 years complaining of nocturia. Patients were given 0.2mg oral desmopressin tablets at bed time and a voiding diary was kept before, during, and after treatment . Results: nocturnal polyuria was present in 80%(24 patients) of the study population and 96% of them(23 patients) improved clinically on desmopressin therapy, with no serious side effects detected. Patients with normal nocturnal urine output did not improve on treatment. conclusion: Oral desmopressin is an effective therapy for patients suffering from nocturia due to nocturnal polyuria. However, after stopping treatment all patients experienced the same clinical manifestations as before treatment.