Background: Despite many modifications to the extended latissimus dorsi flap, its use in autologous breast reconstruction remains limited because of insufficient volume and donor-site morbidity. Through a detailed analysis of the deposition of back fat, this study describes a low transverse extended latissimus dorsi flap harvest technique that increases flap volumes and improves donor-site aesthetics. MethodS: Eight fresh cadaver hemibacks were used to identify the anatomical location of the fat compartments. Correlation between the fat compartments and the fat folds was made using photographic analysis of 216 patients. Retrospective case note review was conducted of all patients who had a low transverse extended latissimus dorsi flap performed by the senior author (M.S.-C.). Results: Cadaveric dissection and photographic analysis confirmed the presence of the four distinct fat compartments in the back. The lower compartments 3 and 4 were the most frequently identified and the largest, with mean values of 367 cm and 271 cm, respectively. The clinical series comprised eight high-body mass index patients who underwent 12 pure autologous breast reconstructions using the low transverse skin paddle harvest technique. Donor-site complications included partial dehiscence (n = 2) and minor infection (n = 3). There were no instances of seroma, and fat necrosis (<5 percent) occurred in one breast. Conclusions: The low transverse skin paddle extended latissimus dorsi flap is reliable and provides sufficient volume for purely autologous breast reconstruction with low donor-site morbidity and improved body contouring for a select group of patients. The authors' initial experience with high-body mass index patients shows promising results with this flap in a challenging group.