To investigate the relationship between the sex steroid receptor (estrogen receptor [ER] and progesterone receptor [PR]) status and the cell proliferation kinetics during the menstrual cycle in normal and neoplastic epithelium of the uterine cervix, immunohistochemical localization of ER, PR, and cell proliferation-associated antigen, Ki-67, was investigated in 35 normal cervical specimens, 3 condylomas, 26 cervical intraepithelial neoplasia (CIN) samples, and 22 invasive squamous carcinoma samples. The presence of human papillomavirus (HPV) DNA was also studied. In the normal cervix, basal cells were usually ER positive, PR negative, and Ki-67 negative throughout the menstrual cycle. Parabasal cells were ER positive and PR negative in the follicular phase, but ER negative and PR positive, and Ki-67 positive in the luteal phase, and Ki-67-positive cells increased in number in the luteal phase. In contrast, PR positivity was observed in the cells of condyloma (2 of 2 cases), CIN (19 of 26 cases), and invasive squamous carcinoma (13 of 22 cases) irrespective of the menstrual phase. Moreover, most neoplastic cells containing HPV DNA type 16/18 were ER negative, whereas several lesions containing HPV DNA type 31/33/35 were weakly ER positive. Many Ki-67-labeled cells were observed in the neoplastic lesions. These results suggest that reduced ER expression and increased PR expression are associated with the proliferation of normal cervical squamous epithelium, and this proliferation-related receptor status, which is probably induced by HPV infection, is usually expressed in neoplastic cervical squamous cells.