Mares were subjected to frequent examinations by diagnostic ultrasound and data were collected over two breeding seasons on 140 Arabian mares (6-22 years old). The cumulative pregnancy rate at 38 day postovulation was 76. 5% and the pregnancy rate per cycle was 75%. The average number of cycles per conception was 2 with an average of 2.28 inseminations per concepted cycle. The incidence of early embryonic death was 8.5%. The incidence of endometrial cysts; prolonged diestrus; behavioral anestrus, ovarian tumors, uterine tumors and pyometra were 2.71, 6.67, 4.17, 1.25, 1.25 and 3.45% respectively. Ultrasound scanning of normal ovaries and uterus were done. The follicular diameters were 22.2 ±0.06, 32.5±0.07, 40.2±0.02 and 41± 0.0 1 mm at the 1st, 2nd, 3rd and 4th days of estrus respectively. The average size of the follicles prior to ovulation was 45.2±0.03 mm. Early pregnancy diagnoses as well as diagnosis of certain reproductive disorders were done using diagnostic ultrasound. It was concluded that, ultrasound is a good tool for judgment the reproductive performance in mares and its use is safety and did not impair the reproductive efficiency.