A multi-center retrospective survey was conducted to evaluate the incidence and types of hemostatic complications occurring in children with acute lymphoblastic leukemia (ALL) during treatment according to the ALL-BFM-90 treatment protocol. All of the BFM-treatment centers (n = 77) were approached and a 95% response rate with information on 1100 patients was obtained. Thrombotic or bleeding episodes occurred in 31 patients (2.8%), 19 of whom had thrombosis and 12 bleeding complications, involving the central nervous system (42%), the subclavian vein (29%), the gastro-intestinal tract, skin, lower extremities or pelvis (29%). Recovery was noted in 28 of 31 patients, while 3 died as a result of hemostatic complications. Bleeding or thrombosis occurred in patients receiving prophylactic substitution with plasma or plasma-derived concentrates (n = 16) as well as in those without substitution (n = 13). The majority of hemostatic complications (90%) occurred during the induction therapy of the treatment protocol, in particular during the period which included simultaneous administration of glucocorticoids and E. coli L-asparaginase. The concurrent administration of E. coli L-asparaginase and glucocorticoids may be an additional risk factor for thromboembolic events during therapy according to the ALL-BFM-90 protocol.