The breeding and rearing of Kintamani Bali dogs have evolved from just keeping them as pets to a dog farming industry. Individual variation in female dog fertility must be detected to manage to breed successfully. Vaginal smear cytology is a low-cost and simple method of determining dog's estrus cycle stages. This study aims to determine the vaginal cytology and receptivity to mating behavior in Kintamani Bali bitch during the proestrus to the estrus phase. The investigation started on the first day of proestrus and continued until the first day of receptivity of mating with a male naturally. The results of this study showed that from the beginning of serosanguinous discharge to early estrus, characterized by a gradual change from initially parabasal and intermediate cells (small then larger) and finally to superficial cells. The onset of estrus is characterized by a predominance of superficial cells and their nucleus disappears and is accompanied by a peak of fully cornified cells. In conclusion, was observed a significant difference in cornified cell identification between the proestrus and estrus phases.