DDAVP (1-desamino-8-D-arginine vasopressin) was administered intranasally to 20 normal persons and blood was collected at various intervals up to 72 h. Plasma concentrations of VIII:C, VIIIR:Ag and fibrinolytic activity were increased by DDAVP with peak levels observed 1 h after the administration. Factors V, IX, XI, XII, XIII, P-APT time, platelets, platelet factor 3, P&P, AT III, alpha 2AP, fibrinogen and FDP were unchanged by the treatment. No side effects or changes in plasma Na or osmolality were observed. The present data demonstrate the selectivity of the effect of DDAVP on the coagulation system and points towards the possibility of using DDAVP in blood donors to increase plasma contents of factor VIII.