Objective:To explore the pathological characteristics of aneurysms of membranous septum (AMS) associated with perimembranous ventricular septal defect by analyzing cell proliferation and survival. Methods:The structure of AMS was analyzed by HE staining. Immunohistochemical staining of Ki67 and phosphorylated Akt (pAkt) was performed to identify cell proliferation and survival in AMS. Results:HE staining showed that the number of cells in false AMS was more than that in true AMS,but the extracellular matrices of false AMS were less compact than those of true AMS. Much more Ki67 positive cells in false AMS suggested a more powerful proliferation than true AMS. pAkt staining was only found in endothelial and subendothelial cells in false AMS. Conclusion:False AMS demonstrates stronger ability of cellular proliferation and survival indicating it’s an active tissue.