Transvaginal pelvic ultrasound is a key tool in the examination of the subfertile woman. Cyclical physiological changes in the ovary are clearly identifiable on scan, which can also be used to assess ovarian reserve to counsel patients and plan treatment cycles. Pelvic scanning can also identify a wealth of ovarian and adnexal pathological conditions that influence fertility and may require intervention. This chapter outlines ultrasound assessment of the normal ovary and key ultrasonic features of common pathologies seen in the subfertile woman.