Aim To observe the plaque morphological characteristics and oxidized low density lipoprotei (ox-LDL) expression in the carotid arteries of brain ischemia autopsy cases. Methods Serial sections of the carotid arteries of the 8 cases with cerebral ischemia were taken and the morphology of the plaques were observed microscopically. Twenty stable and unstable plaques were randomly selected to do the immunohistochemical staining for ox-LDL. Computer image analysis system was used to measur the thickness of fibrous cap and the ox-LDL content of the stable and unstable plaques. Results 26(21.5%)of the 121 carotid artery plaques in the 8 cases were unstable plaques;while 95 plaques belong to stable plaques(78.5%)(p<0.01). The thickness of the fibrous cap in unstable and stable plques were 0.2±0.1 mm and 0.5±0.2 mm respectively(p<0.01). The immunohistochemical staining for ox-LDL were positive in both unstable and stable plaques. But the postive area was significantly larger in unstable plaque than that in stable plaques (19.4±3.3 and 14.3±2.5 respectively, p<0.01). Conclusion the carotid arteries consist of unstable and stable plaques. The unstable plaque had a relatively thinner fibrous cap than that of stable plaque and the ox-LDL postivity area was larger in unstable plaque than in stable plaque. This indicates that ox-LDL may bear a close correlation with plaque stability.