Fourteen human lateral incisors with a radicular lingual groove were observed under the scanning electron microscope to explore the communications between the groove and the pulp cavity. Observations showed that accessory foramina could be found not only in the groove, but also in the corresponding wall of the pulp cavity and a cross section. A complete lack of closure of the calcified tissues along the groove, allowing for direct connection of the pulp and the periodontium, was not found in these specimens. Therefore, it is suggested that accessory canals are the main way of communication between the pulp and the periodontium of the incisors with a radicular lingual groove. Because the accessory canals could be found either in the crown part or in the root part of the groove, infectious materials may get into the pulp cavity when there are pathologic conditions either through accessory foramina in the crown part or through accessory foramina exposed by localized periodontitis around the groove.