Abstract: Objective To study the infection of human papillom avirus(HPV)16/18 and its relationship with expres sion of p53 in invasive ductal carcinoma.Methods The expression of HPV 16/18 DNA and p53 in the invasive ductal car cinom a(n=45),breast fibro adenom a(n=20)and normal breast tissue(n=20) were detected with mimunohisto chemistry method and polymerase chainreaction.Results The expression rate of HPV 16/18 DNA and p53 protein in invasive ductal carcinom a(51.1% and 46.7%) were significantly higher than those of in fibroadenom a of breast(15.0% and 10.0%)and normal breast tissue(5.0% and 0%,P < 0.01),and the expression rate in patients with axillary lymphnode metastasis was significantly higher than those without axillary lymphnode metastasis(P < 0.05).The expression rate of p53 protein in creased with TMN staging and there was a positive correlation between HPV 16/18 DNA and p53 protein expression (χ²=6.517,P < 0.05).Conclusion Both HPV 16/18 infection and p53 mutation are involved in the occurrence and pro gress of breast carcinom a and HPV 16/18 infection may be the main factor relative to p53 mutation.