The present study was conducted to detect the ovarian activities of mares using ultrasonography in relation to the different seasons of the year under Egyptian environmental conditions. This study was carried out on 465 clinically healthy and non-lactating mares. The animals were cyclic and showed signs of estrus regularly. The experimental period was extended from January 2014 to December 2016. All mares were examined with ultrasonography for determination of the reproductive status of each mare specially the degree of activity of the two ovaries monthly. The degree of ovarian activity was either inactive or active according to size of follicles. The results were illustrated that the highest ovarian activity of mares was extended from March till July. On contrary, during November, December and January mares were had higher percentages of smooth ovaries than other months throughout the year. In relation to the season, the highest ovarian activity was reached late spring and early summer while, the least ovarian activity was in late autumn and early winter with minimal ovarian activity in winter season. Ovarian activity in mare was found all over the year with the highest ovarian activity in spring and summer and the lowest ovarian activity in autumn and winter. It was concluded that under Egyptian conditions, most mares have the ability to show continue cycling activity throughout the year, however, photoperiod play an important role in the intensity of ovarian activity and reproductive cycle.