The aim of study was to determine the degree of endometrial edema on the days of estrus and ovulation in cyclic Purebred Arabian mares. For this purpose, 20 purebred Arabian fertile mares, aged from 5 to 12 years were used between April and May. All of the mares were observed during at least one estrous cycle. The ovulation day was accepted as day 0 (dO). The mare were observed and examined for estrus from d 14 until detection. During the same period, the uterus of all mares was examined using ultrasound and the degree o( edema was graded. On the estrus day, edema scores were as following, grade 3 (20%, n=4), grade 2 (65%. n=13), grade 1 (15%, n=3). On the ovulation day edema score was grade 0 in 16 mares (%80) and other 4 mares (%20) had grade 1 edema. After the ovulation day, all of mare had no edema in uterus as seen during the diestrus. As a result, grading the edema in the uterus could be a useful method in predicting the day of estrus and ovulation along with the use other estrus detection methods (teaser stallion, vaginal examination and follicular growth) in purebred Arabian mares.