Introduction: A sagittal split of the mandible is a well established surgical procedure nowadays. A sagittal split however that is performed in a previously reconstructed mandible is a rare procedure. Case Report: A 37 years old patient presented with an odontogenic keratozystic tumor of the mandible. After surgical treatment - preserving the inferior alveolar nerve- reconstruction was achieved with a cortical iliac crest bone graft. After this surgery, however, a unilateral mandibular prognathia developed. Clinically the patient presented with a class III occlusion on the right side and a lateral shift of the dental midline of 3 mm to the left, as well as an edge to edge bite on the left. Therefore, eight months after the initial resection of the tumor and the reconstruction, we carried out a unilateral mandibular split in the reconstructed bone with as little bone denudation as possible. The osteotomy was fixed with two mini-plates. Wound healing was uneventful. A stable clinical result with class I occlusion was achieved. X-rays showed neither an atrophy nor an osteolysis of the grafted area. Six months later screws and plates were removed and three dental implants were inserted. After osseointegration of the implants masticatory rehabilitation was achieved by a prosthetic dental suprastructure of three single-crowns. Conclusion: Sagittal split ostetotomy in the angular region of the mandible is possible even in reconstructed bone after free bone grafting from the iliac crest, if excessive bone denudation is avoided. In this case the graft lost none of its original dimensions. Keywords: sagittal split osteotomy, unilateral, iliac crest bone graft