Abstract: Objective To study the Bax expression in stable and unstable carotid atheromatous plaques and its clinical significance. Methods Twenty-five carotid atheromatous plaque specimens were divided into stable group（n=14）and unstable group（n=11）.Liver transplantation donors served as a control group（n=6）.Expression of apoptotic Bax was detected by immunohistochemistry（IHC）,in situ hybridization（ISH）and in situ TdT dUTP nick end labeling（TUNEL）,respectively. Results Positive expression of Bax in stable carotid atheromatous plaques was detected in 5 cases by ICH,in 5 cases by ISH,and in 4 cases by TUNEL,respectively,while in unstable carotid plaques was detected in 10 cases by IHC,in 11 cases by ISH,and in 9 cases by TUNEL,respectively（P＜0.01）.The intensity of Bax（+）cells detected by IHC and ISH was 8.63±2.62 and 10.32±3.12 in stable carotid atheromatous plaques,and 122±21.64 and 152±23.35 in unstable carotid atheromatous plaques,respectively（P＜0.01）.No expression of Bax was found in control group. Conclusion A high expression level of Bax in unstable carotid atheromatous plaques is one of the factors influencing the molecular pathology of stability of carotid atheromatous plaques and neurological clinic events.Control of its expression in different stage of carotid atherosclerosis may provide targets in gene therapy for carotid atherosclerosis.