The authors have observed clinically and histopathologically on two cases of rhabdomyosarcomas occurred in the oral cavity. The results were as follow: 1. A case of adult pleomorphic rhabdomyosarcoma, involving the right mandibular third molar area of 52 year old male, revealed pathological fracture of the right mandibular angle area. Microscopically, sections of this tumor showed cross striations by staining of phosphotungstic acid hematoxylin. 2. A case of embryonal alveolar rhabdomyosarcoma, involving the right buccal area of one year and ten months old female, revealed severe bone destruction on the right mandibular body area. Microscopically, sections of this tumor did not show cross striations.