XprESS Maxillary Balloon Dilation Study

Inclusion Criteria: 1. Be at least 18 years of age. 2. Must have uncomplicated sinusitis of the maxillary sinuses with or without anterior ethmoid disease. 3. Meet EITHER the Anthem Coverage Guideline OR BlueCross BlueShield of North Carolina Corporate Medical Policy for medically necessary functional endoscopic sinus surgery (FESS) to treat uncomplicated sinusitis. 4. Have a CT scan within 6 months prior to enrollment. 5. Be mentally and physically capable (as per physician discretion) to participate in the investigation. 6. Be willing and able to sign the study-specific informed consent prior to any study-related procedures. 7. Be willing and able to undergo balloon dilation in the clinic setting. Exclusion Criteria: 1. Have evidence of posterior ethmoid, sphenoid or frontal sinus (excludes presence of mucous retention cysts) disease requiring endoscopic sinus surgery or balloon dilatation. 2. Have presence of features consistent with sinus fungal disease. 3. Have evidence of gross polypoid disease within any of the sinuses or within the infundibulum. 4. Require concurrent nasal surgery (eg, septoplasty, turbinate reduction, etc). 5. Have previous sinus surgery (eg, sinus surgery or balloon sinuplasty). 6. Have nasal surgery (eg, septoplasty, turbinate reduction) performed within 3 months prior to enrollment. 7. Have any anatomical anomaly (ie, severe septal deviation) preventing transnasal access to the maxillary sinus outflow tract. 8. Have a history of primary ciliary dysfunction. 9. Have hemophilia. 10. Be currently undergoing, or have undergone in the past 6 months, chemotherapy for cancer or radiation therapy in the head or neck region. 11. Have a history of cystic fibrosis. 12. Have Sampter's Triad (ie, defined as having all 3 of the following: aspirin sensitivity, asthma, and sinonasal polyposis). 13. Have known sinonasal tumors or obstructive lesions. 14. Be pregnant at the time of enrollment. 15. Be unable to stop anticoagulant medication (eg, warfarin) until the International Normalized Ratio (INR) is below 1.5. 16. Be unable to stop antiplatelet (eg, clopidogrel, aspirin, etc.) for at least 7 days prior to study procedure. 17. Be currently participating in any other drug or device clinical studies excluding postapproval or marketing registry studies.