In recent years, gluteal fat augmentation has exhibited some of the most significant growth among all plastic surgery procedures. However, as the popularity of and media attention to gluteal fat augmentation continue to rise, reports of fatalities, largely attributed to fat embolism, have raised valid concerns. Many plastic surgeons inject fat in the intramuscular plane and claim better graft take in the muscles and the possibility of injecting more volume in the gluteal region. Because of the large caliber of vessels, subcutaneous fat augmentation has been a preference of many. However, the long-term outcome of fat injected into the subcutaneous layer has been questionable, and there is a lack of prospective quantitative studies of subcutaneous-only fat grafting. Therefore, the authors evaluated the long-term maintenance of gluteal adipose thickness when fat was injected only subcutaneously. Fifty consecutive female patients were evaluated in this prospective clinical study. All patients underwent gluteal fat augmentation in the subcutaneous plane only. Ultrasound analysis of the adipose tissue thickness of the gluteal region was performed preoperatively, immediately postoperatively, and at 12 months postoperatively. Immediate postoperative measurements revealed an average increase in gluteal subcutaneous layer thickness of 56.51 percent (range, 39.5 to 108.6 percent) (p < 0.0001). At 12 months postoperatively, the gluteal adipose tissue thickness decreased by an average of 18.16 percent (range, 6.8 to 24.8 percent) (p < 0.0001). Subcutaneous-only gluteal fat augmentation is shown to be as effective as previous studies reporting intramuscular fat injection with regard to long-term fat retention in the buttocks. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Therapeutic, IV.