Injection of 1-deamino-1-monocarb-arginine-vasotocin (0.05 μg/100 g body weight) to alert rats caused increased natriuresis, diuresis, and reabsorption of osmotically free water. Injection of furosemide (0.5 mg/100 g body weight) increased Na+ excretion and did not increase reabsorption of osmotically free water. 1-Deamino-1-monocarb-arginine- vasotocin in molar conversion increased natriuresis by almost 6×104 times more effectively than furosemide. © Springer Science+Business Media, Inc. 2007.