We report a rare case of an ectop ic third molar at the level ofthe osteo niea tal comp lex. A 2 1-year-old man came to us with a left-sided nasal obs truction of 2 years' duration. Comp uted tom ograph y ofthe pa ran asal sinuses reve aled that an aberrant tooth was obstructing the osteotnea tal comp lex and bulging into the ethmo id infundibulum. Opa city of the entire left maxillar y sinus indicated the presence ofan asso ciated cys tic fo rmation. A tran snasal endosco pi c sinus technique was emp loye d to create a large middle meatal antros tomy and to remove the tooth as well as the cystic contents and cys t wall. Path ologic analys is reveal ed that the cys t was denti gerous. Af ter recoveryfront surgery , the pati ent resumed nasal breathing. The endoscopic surg ica l approach used in this case caused less morbidity tha n do the more commo n methods (e.g., the Caldw ell-Luc p rocedure) of remov ing ectop ic teeth fro m the sinus.