Vaginal cytology with behavioral observation was performed in 34 estrous cycles in 16 Miniature Schnauzer dogs to evaluate the its usefulness. The mean duration of proestrus and estrus in Miniature Schnauzer based on behavioral observation and vaginal cytology was $7.58{pm}1.50$ (Mean ${pm}$S.D., range: $5{sim}10$) and $8.46{pm}2.82;(6{sim}17)$ days for proestrus, and $6.97{pm}1.66;(4{sim}10)$ and $10.29{pm}2.61;(6{sim}19)$ days for estrus, respectively. The duration of each phase of the estrous cycle was not significantly different based on between behavioral observation and vaginal cytology. The gestational length from the first day of male acceptance was $66.55{pm}2.91;(64{sim}76)$ days, $57.70{pm}1.92;(54{sim}62)$ days from the first male refusal, and $56.90{pm}1.62;(54{sim}60)$ days from the onset of cytologic diestrus, respectively. Vaginal cytology during the estrous cycle were significantly characteristic of large intermediate cells in proestrus, anuclear cells in estrus, small intermediate cells in diestrus, and parabasal cells and small intermediate cells in anestrus (p<0.001), respectively. Cornification index (CI) by vaginal cytology was higher in proestrus ($69.90{pm}1.44%$) and estrus ($91.35{pm}1.09%$), then it was decreased in diestrus ($13.53{pm}1.28%$) and anestrus ($1.16{pm}1.26%$).