AN experimental mouse model of thromboembolic stroke is presented, in which standardized fibrin-rich emboli (15 0μm diameter, 1.5 mm or 4 mm length) are injected into the internal carotid artery. Injection of six or eight 1.5 mm clots (corresponding to 0.16 or 0.2 μl clot material) led to a variable decrease in laser Doppler flow (LDF), but did not result in reproducible infarcts of the middle cerebral artery (MCA) territory, as determined by triphenyltetrazolium chloride (TTC) staining 2 4 h after embolization. Injection of ten 1.5 mm clots (0.2 7 μl) or four 4 mm clots (μl), however, caused a persistent LDF decline to about 20–30% of baseline and led to reproducible infarcts covering the entire MCA territory. The method establishes a clinically relevant, reproducible stroke model for the study of molecular mechanisms of ischemic brain injury in genetically engineered mice.