The purpose of the study was to investigate with the aid of stereosialography and orthopantomography, the connection between developmental mandibular bone defects and the submandibular salivary gland. In sialographies on seven patients, there were two cases in which the contrast medium was found, with certainty, to fill the lobe of the submandibular salivary gland in the area of the bone defect. In four cases the contrast medium ended in the immediate vicinity of the defect. In one case no conclusive result was obtained. The results of the study suggest that the developmental mandibular bone defect and the lobe of the submandibular salivary gland being in close contact with the lingual surface of the mandible have a probable etiologic causal connection, at least in a number of cases.