The use of ultrasound to study ovarian function was established by our group. Ultrasound measurements of follicular diameters were found to be helpful for assessing follicular growth and development and for diagnosing and treating infertile women. Because of difficulties in ovarian visualization (differentiation between a more lateral part of the uterus and the ovary), the definition of a reference plane is necessary, especially to make this new technique reproducible. On the basis of the anatomic situation, we believe that it is possible to demonstrate ovarian vessels within the infundibulopelvic ligament. Using a compound scanner and a combined method of B mode, A mode, and TM mode, it should be possible to demonstrate such structures, and they should be useful as a reference plane. Our observations were confirmed in more than 2,500 examinations.