European investigators have reported on the efficacy of l-deamino-9-D-arginine vasopressin (DDAVP) in von Willebrand’s disease (vWD) and mild hemophilia A. We have thus evaluated the effects of a single intranasal dose of DDAVP (200ugm of the more dilute form available in the U.S.), in 12 individuals with vWD and in 4 with moderate hemophilia A. Crossed immunoelectrophoresis of VIII: RAg demonstrated normal electrophoretic mobility in each of the vWD subjects. Components of the factor VIII system (VIII: C, VIII: RAg, VIII: R Cof.) were assayed pre - and 90 and 180 minutes post- DDAVP. Each of 11 subjects with mild or moderate vWD had an increase in VIII: C activity (avg. 2X increase), 8 of 11 had an increase in VIII: R Cof, and 9 of 11 had an increase in VIII: RAg. The twelfth vWD subject, who had severe vWD, had no rise in any of these components. Of 4 vWD subjects who had pre- and post-DDAVP template bleeding times (BT) performed, the only one who had a prolonged baseline BT showed a normal BT 90 minutes post-DDAVP. One vWD subject, in whom we had documented an increase in all F. VIII components after DDAVP, later underwent dental extractions 90 minutes after DDAVP. No excessive bleeding was noted. Four individuals with moderate hemophilia A (baseline VIII: C values of 0.02-0.10 u/ml) were also studied. Three had a rise in all components of the factor VIII system post-DDAVP while the fourth did not. No undesirable side effects were noted in any of the 16 subjects who received DDAVP. We conclude that even the more dilute form of DDAVP available in the U.S., when given intranasally, results in transient improvement in selected individuals with vWD or moderate hemophilia A. This drug thus warrants further study as an alternative to blood components in the management of vWD, as well as in mild and moderate hemophilia A.