As part of an investigative protocol requiring serial liver biopsies in patients with Type I Gaucher's disease who were receiving enzyme replacement therapy, we gave 11 patients a total of 15 infusions of DDAVP (0.3 μg/kg IV) and measured the Simplate bleeding time pre- and postinfusion. All patients were thrombocytopenic (one patient 100–150,000; seven 66–99,000; and three 50–65,000/μl). Nine of 15 infusions resulted in at least a 2-min shortening of the bleeding time; in 6/11 infusions in which the platelet count was >65,000, the bleeding time shortened to ≤10 min, in 1/11 it shortened ≥2 min but not to ≤10 min. In only 2/4 infusions given to patients with platelet counts <65,000 did the bleeding time demonstrate any significant shortening. None of the six liver biopsies performed in the patients whose bleeding time shortened to ≤10 min resulted in any significant bleeding; blood products were not transfused either pre- or postprocedure. These limited data demonstrate that a high percentage of patients with platelet counts of 65–100,000/μl can manifest a significant shortening of bleeding time following a standard infusion of DDAVP, and that in approximately half of these patients the bleeding time will shorten enough to safely allow the performance of a liver biopsy without the need for prophylactic transfusion of blood products.