Objective: To describe endoscopic management of frontal sinus cerebrospinal fluid (CSF) leaks. Study design: Retrospective. Methods: We reviewed all frontal sinus CSF leaks treated using an endoscopic approach at our institutions from 1998 to 2003. CSF leaks originated immediately adjacent to or within the frontal recess or frontal sinus proper for inclusion in the study. Data collected included demographics, presenting signs and symptoms, site and size of skull-base defect, surgical approach, repair technique, and clinical follow up. Results: Seven frontal sinus CSF leaks in six patients were repaired endoscopically. Average age of presentation was 45 years (range 25-65 years). Aetiology was idiopathic (three), congenital (one), accidental trauma (one), and surgical trauma (two). All patients presented with CSF rhinorrhea; two patients presented with meningitis. Four defects originated in the frontal recess, while two others involved the posterior table and frontal sinus outflow tract. Four patients had associated encephaloceles. We performed endoscopic repair in all six patients with one patient requiring an adjuvant osteoplastic flap without obliteration. All repairs were successful at the first attempt with a mean follow up of 13 months. All frontal sinuses remained patent on both post-operative endoscopic and radiographic exam. Conclusions: Endoscopic repair of frontal sinus CSF leaks and encephaloceles can be an effective method if meticulous attention is directed toward preservation of the frontal sinus outflow tract, thus avoiding an osteoplastic flap and obliteration. The major limiting factor for an endoscopic approach is extreme extension superiorly or laterally within the posterior table beyond the reach of current instrumentation.