Brain hemorrhage is a feared complication of early anticoagulation therapy in patients with cardioembolic brain infarction. We describe nine patients with cardioembolic stroke who experienced clinical deterioration associated with computed tomography-documented hemorrhagic transformation. The clinical features of these nine patients combined with 15 previously reported cases were analyzed to determine factors associated with hemorrhagic worsening. Patient age, embolic source, and intensity of anticoagulation were not associated with hemorrhagic worsening. Large infarct size and initiation of anticoagulation after early (less than 12 hours) computed tomography were associated with hemorrhagic transformation and clinical worsening in patients who received anticoagulation therapy.