Systemic mastocytosis is a rare and clinically fascinating disorder that usually involves the skin and hematopoietic tissues. We report a patient with systemic mastocytosis involving the mandible who had no other presenting bone lesions on scintigraphic exam. After noting the radiographic emergence of this osteolytic jaw lesion over a 6-month interval, a biopsy of the lesion was performed, and histologic and electron microscopic studies completed. It is believed that this is the first documented case of mastocytosis to involve an oral-maxillofacial bone. Careful preoperative evaluation and clinical management were conducted to avoid potentially life-threatening complications. A discussion of this condition and strategies for diagnosis and patient management are presented.