The treatment of the haemorrhagic tendency of acute renal failure remains unsatisfactory. To investigate a potential new therapy, 8 patients with acute renal failure and prolonged bleeding times received an infusion of 1-deamino-8-d-arginine vasopressin (0.4 microgram/kg). This resulted in significant shortening of the bleeding time at 1 and 2 hours post-infusion. The beneficial effect on bleeding time had largely disappeared by 8 hours. Pre-infusion Factor VIII activities were either within the normal range or mildly increased and a tendency to further elevation was noted post-DDAVP. In contrast, no alteration in platelet count or haematocrit was observed. No adverse effects were reported, and no significant change in heart rate, blood pressure or plasma osmolarity was noted.