Background. The amount of postoperative maxillary relapse of two different bone graft materials after Le Fort I osteotomy were compared in this study. Objectives. The aim of this study is to compare postoperative maxillary relapse rates using heterologous and autologous graft materials after Le Fort I osteotomy. Material and Methods. A total of 80 patients who had developmental malocclusion were analyzed retrospectively in this study. Twenty nine (36.2%) and 51 (63.8%) patients underwent Le Fort I osteotomy, and Le Fort I and bilateral sagittal split ramus osteotomy (two-jaw surgery), respectively. Forty two (52.5%) maxillary bone gaps were filled with heterologous bone grafts (group A) and 38 (47.5%) were filled with autologous bone grafts (group B) after Le Fort I osteotomy. The cephalometric graphics and measurements were taken before (T1), 1 week after (T2), and 1 year after (T3) the surgery. The results were documented and determined by the Dolphin imaging 10.5 (Dolphin Imaging, Chatsworth, Calif.) computer program for skeletal relapse. Whether or not the relationship between group A's and B's maxillary relapse rates was evaluated in the postoperative period. Results. It was observed that both graft materials have positive effects on maxillary relapse rate in the postoperative period. When the groups are compared to each other, the relapse rates were similar between group A (8.3%) and group B (10.8%) (p > 0.05). Conclusions. Heterologous bone graft material (Osteoplant ® -Flex) is thought to be a good alternative to autologous grafts in decreasing the relapse rates and reducing the morbidity of the donor area of the patients who underwent Le Fort I osteotomy (Adv Clin Exp Med 2015, 24, 2, 341-348).