We present a case of fatal mesenteric vein thrombosis (MVT) associated with L-asparaginase (L-asp) therapy and temporally related to cryoprecipitate infusion, in an adult with acute lymphoblastic leukaemia (ALL). Cryoprecipitate was given on two consecutive days to raise a low fibrinogen level of 0.7 g/L, in the presence of severe thrombocytopenia and mucocutaneous bleeding. The thrombotic event presented as sudden abdominal pain a day after the second cryoprecipitate infusion, which raised the fibrinogen to 1.5 g/L. Concurrent levels of antithrombin III (AT III), protein C (PC) and protein S (PS) were very low. The patient died after laparotomy and wide resection of gangrenous bowel. We believe this is the first reported case in the English literature of a patient who developed mesenteric venous thrombosis during L-asp therapy, and once more we advise caution in using conventional blood products, especially cryoprecipitate, and recommend restricting the use of cryoprecipitate and fresh frozen plasma (FFP) to the treatment of serious hemorrhagic manifestations, until new effective and safe therapies are available.