The records of 32 cancer patients who were treated with heparin sodium and warfarin sodium for thromboembolic disease were reviewed. Standard techniques for anticoagulation were neither safe nor effective. Sixteen patients experienced 21 different hemorrhagic complications. Eight patients had major hemorrhages that led to cessation of therapy or death. Six of 32 patients had pulmonary embolisms while receiving anticoagulants. It is suggested that venous interruption may be a safer and more effective method of prophylaxis against pulmonary embolism in cancer patients.