Abstract: Objective To study the expression of Bcl-2 gene in human carotid atheromatous plaques and its influence on stability of atherosclerotic plaques. Methods Forty-two samples of carotid atheromatous plaques taken in endarterectomy were divided into stable group(n=19) and unstable group(n=23) according to their pathological typing.Eight samples of aortic artery and its branches taken from hepatic transplantation donors served as a control group.Expression of Bcl-2 was detected by immunohistochemistry(IHC) and in situ hybridization(ISH),respectively. Results IHC and ISH showed that the bcl-2 was expressed in unstable plaques from 20 and 9 patients,in stable plaques from 11 and 4 patients(P<0.05),and in vascular smooth muscle cells,macrophage cells,endothelial cells and foam cells.The number of Bcl-2 positive cells was 122±28.84 and 258±29.93 in unstable plaques,and 12.93±4.66 and 11.32±6.15 in stable plaques,respectively,with the Bcl-2 positive cells mainly concentrated in the shoulder area where inflammation cells accumulated.The expression level of Bcl-2 was significantly higher in unstable plaques than in stable plaques(P <0.01).No expression of Bcl-2 was found in control group. Conclusion The expression level of Bcl-2 is higher in unstable plaques than in stable plaques and is,thus,an anti-apoptotic and atheromatous plaques-maintaining factor of stability.