The inframammary fold (IMF) is a critical structure affecting the aesthetics of the breast, yet the anatomy and location of the IMF remain controversial. The purpose of this study was to quantitatively evaluate the thickness and location of IMF utilizing magnetic resonance imaging (MRI).The MRI images of 240 breasts from 120 Asian women were analyzed. The quantitative measurements consisted of breast width, breast projection, nipple to inframammary fold, breast volume, IMF tissue thickness, and IMF position. The IMF position was evaluated by referring to the ribs, as well as measuring the distance between IMF and the inferior of the fifth rib.The mean values of central thickness, medial thickness, and lateral thickness were 1.50±0.59, 1.46±0.60, and 1.76±1.04 cm, respectively. IMF central thickness demonstrated a moderate positive correlation with breast projection (r=0.559, P<0.001) and breast volume (r=0.523, P<0.001). The proportions of IMF located at the fourth intercostal, the fifth rib, the fifth intercostal, the sixth rib and the sixth intercostal were 5.8%, 29.2%, 43.3%, 20.4% and 1.3%, respectively. The average distance between IMF and the inferior of the fifth rib was 0.69±1.40 cm. 60.0% of women had near-symmetrical IMF, while 17.5% had left higher IMF and 22.5% had right higher IMF.This study used MRI to quantitatively assess the anatomy of IMF. The detailed knowledge of IMF would facilitate the ideal aesthetic outcome of mammaplasty.2023 Gland Surgery. All rights reserved.