A high frequency of disseminated intravascular coagulation (DIC) in adult acute lymphoblastic leukemia (ALL) has been reported; however, its clinical relevance and characteristics have not been fully determined. We studied 67 adults with newly diagnosed ALL between 1982 and 1996 to clarify these questions. DIC was diagnosed in ten of 64 patients (16%) who underwent coagulation study at presentation and in 14 of 40 patients (35%) screened for DIC within 7 days after starting remission induction therapy. Overall, 24 of 67 patients (36%) had DIC during this period. Hemorrhagic symptoms were generally mild, while two patients required red blood cell transfusions. Patients who developed DIC had higher white blood cell counts and more frequently a palpable spleen than those who did not. There was no difference in age, French-American-British subtype, karyotype, immunophenotype, lactate dehydrogenase level, percentage of blasts in bone marrow, or frequency of lymphadenopathy or hepatomegaly between patients who had DIC and those who did not. Fibrinolysis tended to be milder in DIC complicating ALL than in that complicating acute promyelocytic leukemia; however, there was no difference in other coagulation parameters between these two subtypes. An etiological link between CD34 expression in common ALL patients and DIC was suggested.