The prolonged bleeding times of 12 patients with chronic renal failure were significantly shortened at 1 and 2 h after an infusion of 0.4 microgram/kg 1-deamino-8-D-arginine vasopressin (DDAVP). In 5 of these patients, the bleeding times 24 h after infusion had returned to approximate baseline values, suggesting that the effect of DDAVP is a temporary one. The levels of factor VIII coagulant activity, factor VIII related antigen activity, and factor VIII ristocetin cofactor activity were all normal or elevated prior to infusion, and a tendency to further elevation, although significant only for the factor VIII ristocetin cofactor activity, was observed after infusion of DDAVP. The latter observation suggests that the effect of DDAVP infusion on the bleeding time is unrelated to alteration of factor VIII activities.