Background: Frontal sinus cerebrospinal fluid (CSF) leaks have traditionally been repaired via open procedures (eg, osteoplastic flap or cranialization). Advancements in instrumentation, technique, and experience have improved the feasibility of repairing frontal sinus skull-base defects using an endoscopic approach. This study describes endoscopic closure of frontal sinus CSF leaks focusing on management, surgical technique, and outcomes. Methods: Prospective evaluation of patients with skull-base defects involving the frontal sinus was performed. Demographics, size of skull-base defect, length involving the posterior table, successful closure, frontal sinus patency, and complications were recorded. Results: Over 3.5 years, 37 patients (average age 46 years) were treated for CSF leaks involving the frontal sinus by a single otolaryngologist. Etiologies included spontaneous (13), tumor (13), and trauma (11). Average defect size (length vs width) was 16.9 mm × 10.7 mm and average length involving the posterior table was 6.9 mm (range, 1-30 mm). Success rate on first attempt was 91.9% (34/37), but improved to 97.3% on subsequent endoscopic revision. One patient required a cranialization. The average follow-up was 48 weeks. The nasoseptal flap was used for reconstruction in 27 patients. A Draf III procedure (ie, bilateral resection of the frontal sinus floor) was required in 14 subjects. Three patients were referred as a result of unsuccessful closure following cranializations; their CSF leaks were successfully repaired using endoscopic approaches. Two individuals required a subsequent endoscopic frontal sinus procedure, but have maintained long-term patency following revision. Conclusion: Frontal sinus CSF leaks were successfully closed in 97.3% of individuals. Our data supports the routine use of endoscopic repair in the treatment algorithm for frontal sinus skull-base defects. © 2012 American Rhinologic Society-American Academy of Otolaryngic Allergy, LLC.