We report a rare case of an ectopic third molar at the level of the osteomeatal complex. A 21-year-old man came to us with a left-sided nasal obstruction of 2 years' duration. Computed tomography of the paranasal sinuses revealed that an aberrant tooth was obstructing the osteomeatal complex and bulging into the ethmoid infundibulum. Opacity of the entire left maxillary sinus indicated the presence of an associated cystic formation. A transnasal endoscopic sinus technique was employed to create a large middle meatal antrostomy and to remove the tooth as well as the cystic contents and cyst wall. Pathologic analysis revealed that the cyst was dentigerous. After recovery from surgery, the patient resumed nasal breathing. The endoscopic surgical approach used in this case caused less morbidity than do the more common methods (e.g., the Caldwell-Luc procedure) of removing ectopic teeth from the sinus.