We retrospectively studied the incidence of recurrent embolization and hemorrhagic complications during a 2-week period after the onset of cardioembolic stroke according to the form of anticoagulation given immediately after the event. Twenty-six patients had full-dose heparin (F/H group), 37 had low-dose heparin (L/H group), 81 were treated with warfarin potassium (W group), and 20 were treated with antithrombin III (AT group), while 227 patients (non-A/C group) received no anticoagulation. The incidence of early recurrence was significantly lower in all anticoagulated groups (3.8% in the F/H group, 5.4% in the L/H group, 3.7% in the W group and 0% in the AT group), than that in the non-A/C group (20.3%). There were no significant differences in the incidence of hemorrhagic complications among the groups. Not only full-dose anticoagulation but also antithrombin III or low-dose heparin therapy may prevent the recurrence of embolization in acute cardioembolic stroke.