Abstract: Twelve patients aged 14-48 years （6 famales, 6 males） with diabetes insipitus were reated with 1-deamino-8-D-arginine vasopressin （DDAVP） under double-blind study for 5 days. he 4-hour urine was collected and its volume and osmolarity were measured every day during herapy. The results showed that there was a marked decrease in urine output and increase in rinary osmolarity during treatment. DDAVP was well tolerated by the patients and it didn’t ause changes in blood presure or heart rate.