Rectal temperature was recorded from 22 mares at 0700, 1500 and 2300 h daily for seven days pre-partum and one day post partum. A circadian variation in rectal temperature was present with the lowest temperature recorded at 0700 h. Because of this, the mares were divided into three groups based on time of parturition; those foaling between 0700 and 1500 h (n=2); between 1500 and 2300 h (n=13); and between 2300 and 0700 h (n=7). On the day prior to delivery (Day −1) the circadian pattern was absent because the nocturnal increase did not occur. A significant decrease in temperature was recorded prior to parturition in the group foaling between 1500 and 2300 h. A distinct decrease in temperature occurred in the majority of mares in the other two groups but this was not statistically significant. After parturition, rectal temperature increased to supranormal levels before returning to normal.