Dentigerous cyst originates through alteration of the reduced enamel epithelium after the crown of the tooth has been completely formed. Since the first description of the dentigerous cyst by Albinus in 1754, many cases of aberrant tooth in the maxillary sinus and nasal cavity have been reported. The author has recently experienced a case of a large dentigerous cyst in left maxillary sinus due to unerupted wisdom tooth. This cyst was removed successfully by means of Caldwell-Luc's approach without facial disfiguration or any other complications.