We report our experience with the incidence of adverse events during the use of Stimate brand intranasal desmopressin acetate (IN DDAVP) for patients with haemophilia A (HA) or von Willebrand disease (vWD) after noting two severe adverse events in one adult patient. All patients with documented vWD (type 1 or 2 A) or haemophilia A (mild, moderate or symptomatic carrier) from the Emory Comprehensive Hemophilia Center who had IN DDAVP challenge testing or were using Stimate for treatment of bleeding were evaluated for adverse events by patient report or nursing observation of clinical signs and symptoms. Forty patients were studied. Sixty-eight per cent (27/40) experienced clinical signs and/or symptoms. The majority of these symptoms were mild, however several patients reported moderate to severe side-effects and one adult patient required medical intervention for symptomatic hyponatraemia. In our experience, two-thirds of patients tested experienced adverse signs and/or symptoms with the use of Stimate; considerably higher than that reported from preliminary results in the literature. Young age did not correlate positively with adverse reactions. Severe adverse events requiring medical intervention were rare, however symptoms such as moderate to severe headache, nausea, vomiting and weakness may necessitate evaluation for hyponatraemia. This is the first report of symptomatic hyponatraemia in an adult patient with recommended dosing of Stimate. Side-effects may be minimized if patients adhere to instructions regarding fluid intake and composition while using IN DDAVP.