AbstractTwenty‐one patients with prolonged bleeding times secondary to inherited disorders of platelet function and eight patients with prolonged bleeding times secondary to acquired platelet dysfunction were given 0.3 μg per kilogram of DDAVP, 1‐deamino‐8‐D‐arginine vasopressin, intravenously. Sixteen of twenty‐two DDAVP trials in patients with inherited platelet dysfunction (73%) and seven of the nine DDAVP trials in patients with acquired platelet dysfunction (78%) resulted in normalization or shortening of the prolonged bleeding times by at least 4 min. The bleeding time response did not correlate with changes in the levels of von Willebrand factor (vWf) antigen or ristocetin cofactor activity, nor was it associated with changes in vWf multimeric analysis or in vitro platelet aggregations following the administration of DDAVP. Shortening of the bleeding time with DDAVP was seen in patients with a failure to release/storage pool type defect, thromboxane synthesis type defect, Bernard‐Soulier syndrome, Glanzmann's thrombasthenia, the May‐Hegglin anomaly, liver disease, nonuremic renal disease, myelofibrosis, and T