A high incidence of disseminated intravascular coagulation (DIC) in adult patients with acute lymphoblastic leukemia (ALL) is reported. However, studies comprising both childhood and adult patients are sparse and the clinical relevance of DIC in ALL patients has been a conflicting issue. Coagulation profiles at presentation and within seven days after starting remission-induction therapy of 44 childhood and 51 adult ALL patients were studied. At presentation, two childhood (5%) and 11 adult (22%) patients had DIC (p<0.05). After starting therapy, four of 27 childhood (15%) and 14 of 33 adult (42%) patients screened for coagulopathy developed DIC (p<0.05). Overall, six of the 44 children (14%) and 25 of the 51 adults (49%) were complicated with DIC (p<0.001). In the adult cases, DIC was more frequently complicated with FAB subtype L2 than L1 (p<0.05). All hemorrhages seen in the childhood cases were minor hemorrhages. In the adult patients, two patients with DIC had WHO grade 3 hemorrhage and the other hemorrhagic complications were minor hemorrhages. While milder induction therapies starting with corticosteroid given for childhood cases should be taken into consideration when comparing the incidences of DIC after therapy, the findings indicated that childhood and adult ALL may differ in the procoagulant characteristics. Morphological distinction between L1 and L2 appears to have relevance in the procoagulant activity in adult ALL. DIC complicating ALL is generally mild, however, sometimes causes severe hemorrhages in adults.