Vasopressin and in particular 1-deamino-8-D-arginine vasopressin (DDAVP) can release factor VIII (FVIII) and tissue plasminogen activator (tPA) to the blood. In the present study DDAVP was injected in conscious dogs which had been preloaded with specific antagonists either against vasopressin's vasopressor response (V1-receptors) or its antidiuretic response (V2-receptors). The presence in the blood of either of the antagonists had no effect on the increase of FVIII or tPA following stimulation with DDAVP. It is therefore concluded that the effect of DDAVP on coagulation and fibrinolysis is elicited via a new class of receptors different from the known V1- and V2-receptors.