A squamous odontogenic tumor (SOT) is rare disease and it is believed to originate from epithelial rests of Malassez of the periodontal membrane. Neither sex nor site predilection in either jaw has been established. Some lesion can be shown in juxtaposition in tooth roots. Although most lesions remain smaller than 2 cm, our cases involved a half of left mandibular ramus. The exact pathogenesis is still unknown. We report a case of SOT including the results of immunohistochemical study of pancytokeratin and p53.