AbstractThe current study aimed to determine if characteristics observed in vaginal cytology during the estrous cycle of female SYT cavies corresponded with proliferation of the vaginal epithelium, characterized by proliferating cell nuclear antigen (PCNA) immunolocalization, and with follicular development at different phases of the estrous cycle. After determining estrous cycle phases by vaginal cytology, females were euthanized at metestrus, diestrus, proestrus, and estrus. Histological study of the vaginal epithelium and ovary were then performed. Immunohistochemistry for PCNA in vaginal tissue at each cycle phase was also performed. Superficial cornified cells and early post‐ovulatory follicles were found at estrus. Few nuclei below the enucleate superficial cells were immunoreactive to PCNA. At metestrus, the vaginal epithelium underwent desquamation and lost the superficial cornified cells; basal and intermediate cells appeared, and the post‐ovulatory follicle formed an early corpus luteum. No PCNA immunoreactivity was observed. At diestrus, the corpus luteum was developed, and the vaginal epithelium contained basal and intermediate cells. There was PCNA immunoreactivity in the cellular nucleus in the germinative stratum of the epithelium. Because of the growth and maturation of ovarian follicles, the vaginal epithelium suffered intense proliferation at proestrus. Vaginal cytology revealed large intermediate cells and nucleated and enucleated superficial cornified cells. In the ovary, mature follicles were present. More apparent immunoreactivity of PCNA in the germinative layer was found. In summary, we inferred that vaginal exfoliative findings matched the proliferation process of the vaginal epithelium. PCNA immunolocalization occurred as well as corresponding follicular development in the ovaries.