Desmopressin (DDAVP) 0.3 µg/kg was infused in 20 uremic patients with prolonged bleeding time. Prior to infusion, the uremic patients had a reduced level of tissue plasminogen activator (t-PA), normal levels of von Willebrand factor antigen (vWF:Ag) and ristocetin cofactor activity (vWF:RCo) and elevated level of factor VIII coagulant activity (FVIII:C). Patients with lower hematocrit or t-PA levels tended to have a longer bleeding time. One hour after DDAVP infusion, the bleeding time was shortened significantly. This improvement was significant in all patient groups irrespective of the high or low initial levels of factor VIII complex components. Plasma levels of FVIII:C, vWF:Ag, vWF:RCo and t-PA all increased significantly. The magnitude of increase in these factors, however, was not significantly correlated with the extent of bleeding time shortening. The multiple regression model for predicting the extent of bleeding time shortening suggested only two variables, viz initial bleeding time and posttreatment FVIII:C activity to be of significance. The present results indicate that the hemostatic response to DDAVP is uniform in uremic patients, regardless of whether the initial activities of factor VIII complex components are high or low. Posttreatment FVIII:C activity appears to play a significant role in the hemostatic action of DDAVP. Furthermore, a depressed fibrinolytic activity was generally observed to concur with the hemostatic defect in uremic patients.