Analysis of 182 patients with chronic disseminated intravascular coagulopathy and malignancy shows common features. Migratory thrombophlebitis occurred in 96 patients while at least a single episode of thrombophlebitis was noted in 113. Seventy-five of the patients bled and 45 had arterial emboli in various organs. Twelve patients had the triad of thrombophlebitis, hemorrhage, and arterial emboli, often sequentially. Hematologic data showed derangements associated with intravascular coagulation, the most prominent of which were hypofibrinogenemia and thrombocytopenia. Other abnormalities included prolonged prothrombin time, increased fibrinogen-fibrin degradation products, decreased levels of factors V and VIII, cryofibrinogenemia, and microangiopathic hemolytic anemia. Forty-one patients had lesions of non-bacterial thrombotic endocarditis at autopsy; 31 of these had arterial emboli during life. None of the lesions were infected. Mitral and aortic valves were most frequently involved. No single mechanism that causes the disseminated intravascular coagulopathy has been identified. However, cell products--secretions and enzymes--and the cells themselves have been proposed as the procoagulant(s) responsible for the syndrome. In addition to treatment of the underlying neoplasm, symptomatic disseminated intravascular coagulopathy should be controlled. Heparin is the drug of choice for treatment of this problem, very little benefit having been observed with warfarin therapy. Long-term use of anticoagulants is potentially feasible for control of chronic disseminated intravascular coagulopathy, but without effective control of the underlying tumor ultimately will be unsuccessful.