BACKGROUND: Postmastectomy radiation therapy has well-defined ill effects on the character of the skin envelope of the breast, most directly causing contraction and elevation of the breast, especially at the inframammary fold (IMF). These effects negatively impact breast symmetry, overall aesthetic outcomes, and patient satisfaction. Though radiation-induced skin changes have been qualitatively described, quantitative changes to the position of the IMF due to radiation have not yet been described. Despite maneuvers to lower the fold when postmastectomy radiation therapy is expected, the reoperation rates have been reported as high as 28%. Delineating numerical values may allow more specific intraoperative adjustments to better approximate the IMF to the pretreatment level. Herein we discuss our analysis of the effect of radiation on IMF position in patients who underwent expander placement and subsequent radiation. METHODS: Patients who underwent breast reconstruction with tissue expanders from January 2015 to October 2019 at UCLA by four attending surgeons were reviewed. Operative reports were reviewed and indicated disruption of the IMF in all patients during mastectomies, requiring resetting of the IMF with suture. Patient inclusion criteria required that patients have corresponding sets of pictures at three timepoints: (1) preoperative (before mastectomy), (2) postoperative (after tissue expander placement and before radiation), and (3) postradiation (before exchange to permanent implant). Photographs were retrospectively analyzed by a single surgeon. In the lateral view, the distance from the acromion to IMF was measured, compared with acromion to elbow, and recorded as a ratio to allow for variation of photographic focal length differences. Changes in IMF from pre- to postradiation were measured as a percentage change. RESULTS: Fifteen patients with appropriate photos over the past year were analyzed of which 10 had pictures at all three timepoints, and 5 had only the last 2 timepoints and were excluded. All operative reports were reviewed verifying that the IMF was disrupted after mastectomy in all group. Fourteen had unilateral radiation and 1 had bilateral radiation, thus 16 breasts were reviewed separately. For the 10 patients with preoperative photos, the IMF ratio from timepoints 1–3 (preoperative to postradiation) was −12.5% + 5.2%, indicating a significant elevation of the IMF following radiation. CONCLUSIONS: Inframammary position after tissue expander placement and radiation reliably elevates approximately 12% above the position of the preoperative fold. This study is the first of its kind to quantitatively measure radiation change elevation on the IMF in tissue expander reconstructions. This finding may be a useful guide for setting the IMF at the time of tissue expander placement and avoid need for the second stage fold lowering at the time of implant exchange.