NuvaRing, a combined contraceptive vaginal ring 54 mm in diameter, offers many advantages over oral contraceptives. To better delineate in vivo placement, we performed MRI to confirm its anatomical position. Two healthy users, one nulliparous and one parous, underwent a series of MRI: preinsertion, immediately postinsertion and after ambulation. Three-dimensional imaging of the human vagina demonstrates that in vivo, NuvaRing is located superior to the urogenital diaphragm (UGD), surrounding the cervix. The superior-most aspect of the ring lies behind (posterior) the cervix, at a level superior to the external os. The inferior aspect of the ring also lies in the vaginal canal above the UGD. The entire cervix rests inside the ring. The preambulation image in the nulliparous woman was the only exception. In this case, the upper portion of the ring was at the level of the lower-mid cervix and the lower aspect below the UGD. After ambulation, the ring moved cephalad and surrounded the cervix. In all instances, ambulation resulted in lower aspect of NuvaRing moving away from the introitus. In vivo, NuvaRing is compressed laterally forming a gentle oval in the anterior-posterior direction (5-7 mm longer than wide), an effect that is seen more in nulliparous women.