Insertion of cotton thread impregnated with beeswax and 20-methylcholanthrene (carcinogen) inside the canal of the uterine cervix in intact and oophorectomized mice results in the expression of dysplasia and carcinoma of the cervical epithelium. Based upon the experimental cervical carcinogenesis observed in this mouse model system, the present study shows distinctly the modulatory effect of tamoxifen on the incidence of cervical carcinoma. Besides this, tamoxifen significantly lenghthens the latent period for both dysplasia and carcinoma in the cervical epithelium. This manifestation was found more marked in oophorectomized animals.