The indications for anticoagulant treatment to prevent cerebral infarction or progression of cerebral infarction are now clear. The indications are: (1) Prevention of recurrent embolization from a cardiac source (long-term anticoaguland treatment). (2) Transient ischemic attacks (particularly vertebrobasilar system) if a surgically accessible causative lesion, polycythemia, and thrombocytosis are not present (anticoagulants for a few months.) (3) Progressing stroke in either systme assuming that the neurological defect is partial and CT scan shows no evidence of bleeding (anticoagulants for a few months.) (4) Rarely, completed stroke (long-term).