A mild bleeding tendency and obstructive urinary tract symptoms of several weeks' duration occurred in two patients. Both were found to have mild to moderate thrombocytopenia and metastatic prostate cancer involving the bone marrow. During hospitalization, both developed gross bleeding requiring transfusion therapy. Results of routine clotting studies were normal but additional tests, consisting principally of a positive test for fibrin monomers and a normal euglobulin lysis time, revealed the presence of chronic disseminated intravascular coagulation. Heparin sodium therapy was successful in stopping the bleeding in both patients. Cryofibrinogen was found in abnormal amounts before and after heparin therapy.