Since the first description of the ectopic tooth by Albius in 1754, there have been reported many cases of either aberrant tooth in the nasal cavity and maxillary sinuses. Rencently, the author experienced an ectopic and full-developed canine tooth, in the left maxillary sinus, which was erupted on the thickened superior-lateral bony wall of the maxillary sinus. Removal surgery with Caldwell-Luc's approach was done satisfactorilly and also added the leratural reviews.