Thrombocytopenia was observed in 15 of 146 cases of clinically acute bovine viral diarrhea virus (BVDV) infection in adult cattle. Platelet counts ranged from 2,000 to 33,000/microliters. Clinically, a bleeding tendency was manifested by bloody diarrhea, petechial and ecchymotic hemorrhage, epistaxis, and abnormal bleeding from injection sites. Coagulation testing (six cases) gave no evidence of disseminated intravascular coagulation. Bone marrow aspirates were suggestive of active marrow necrosis (two cases) or recent repopulation (three cases). Treatment, when given, was supportive and empirical in nature. Six animals experienced complete clinical recoveries; the others died or were euthanatized. Although the pathogenesis of the thrombocytopenia was not definitively determined, thrombocytopenia associated with acute BVDV infection should be considered in the differential diagnosis for cattle with bleeding disorders.