Abstract: Objective 　To study the expression and value of p16 IN K4A and bcl-2 in CIN and cervical squamous carcinoma. Methods 　39 cases of CIN, 24 cervical invasive squamous carcinoma and 20 normal cervical tissues were stained for p16 IN K4A and bcl-2 by immunohistochemistry method. Results 　p16 IN K4A immunoreactivity was absent in all normal cervical tissues, its positive rate in CIN Ⅰwas very low too, but p16 IN K4A expressed almost in all of CIN Ⅱ/ Ⅲand invasive carcinoma. Bcl-2 immunoreactivity in normal cervical tissues was only seen in cells of basal layer. It s positive rate in CIN Ⅲand Ⅰ～Ⅱstage invasive carcinoma were 53. 8 %and 57. 1 % respectively, which positive cells were diffuse and its staining intensity was higher than in normal cervical tissues. It s positive rate in Ⅲ～ Ⅳ stage invasive carcinoma was striking decreased, which positive cells were focal. Conclusion 　p16 IN K4A over expression may be seen as a marker of CIN Ⅱ/ Ⅲand invasive carcinoma which is useful in pathological diagnosis.