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.