Histopathological and histochemical changes in cervical epithelium under influence of oral contraceptives (OCs) were studied comparatively in 100 humans and 30 rabbits. The 100 patients used different types of combined OCs including Ovral, Anovlar, and Primovlar; 50 non-OC users served as controls. Cervical biopsies were obtained for study. The animal experiment consisted of 30 female rabbits divided into 3 groups: Group 1 received Lyndiol 1 for 5 days every week; Group 2 received mini-pills (ethynodiol diacetate, .25 mg) every day without interruption; Group 3 was the control. After 1 year the animals were killed and their cervixes examined. In humans, the ectocervical epithelium revealed increased vascularity and its penetration by perpendicular vascular channels reaching two-thirds of its thickness in 65% of cases. Basal cell hyperplasia was increased in 38% of patients. Vesicles between layers of squamous epithelium were observed in 26% of females receiving OCs as compared with 3% of controls. A single case of mild dysplasia was detected. Vascularity of the endocervical stroma was increased in 83% of OC users compared with 30% of controls. 79% of OC users showed endocervical glandular hyperplasia, the most prominent finding, compared with 22% of controls. Results reported for animal studies reflected those reported in human cervical smears.