Two patients with Trousseau's syndrome experienced frequently recurring concomitant arterial and venous thrombotic events that resulted in sequential amputation and loss of the lower extremities. Serial examination of the blood in the patients demonstrated that these devastating thrombotic events were preceded by severe disseminated intravascular coagulopathy that occurred within an interval of a few hours. Warfarin therapy was without effect in preventing the occurrence of these events. Both patients demonstrated the absolute need for intravenous heparin, which effectively prevented the thrombotic events; when it was discontinued, the immediate consequences were disastrous and resulted in death. Techniques for long-term outpatient heparin therapy are discussed.