Although bleeding complications are relatively common in patients with chronic lymphocytic leukemia, they tend to be related to thrombocytopenia or an acquired clotting factor inhibitor. Chronic lymphocytic leukemia-associated thrombocytopenia, which may also contribute to the hemorrhagic risk, is generally caused by decreased production and immune-mediated destruction. This is the case of a 56-year-old man with longstanding chronic lymphocytic leukemia who developed thrombocytopenia (platelet counts of approximately 50,000/microL) with an associated abnormal platelet morphology. Although the patient did not suffer clinically significant bleeding, several tests of platelet function were grossly abnormal. Electron microscopic examination of the platelets revealed virtually complete absence of dense granules. Platelet aggregation did not occur with adenosine diphosphate (10 microM), collagen (2 micrograms/mL), or ristocetin (1 mg/mL). Doubling the agonist concentrations produced only minimal agglutination with ristocetin. The bleeding time was mildly prolonged at 9.0 and 10.5 minutes. Von Willebrand antigen and ristocetin cofactor levels were normal. Collagen-induced adenosine triphosphate secretion was less than 10% that of a matched normal control. In contrast, platelet force development was virtually normal, reaching 4,800 dynes at 1,200 seconds compared with 5,800 dynes for the healthy control. The patient's clots demonstrated enhanced clot modulus 44,000 dynes/cm2 versus 22,400 dynes/cm2 for the healthy control. The latter finding was primarily because of high fibrinogen concentration. This third report of storage pool disease in a patient with chronic lymphocytic leukemia demonstrates that dense granule release is not required for normal platelet-mediated force development.