Cerebrospinal fluid fistula and endoscopic sinus surgery. Seven cases of cerebrospinal fluid fistulae occurring as a result of endoscopic sinus surgery in a total of 800 ethmoidectomies are discussed, along with 1 case referred for consultation. One cerebrospinal fluid fistula was intrasphenoid, 4 were posterior ethmoid/base of skull, 2 were anterior ethmoid, and 1 was ethmoid cribriform. Six of 8 fistulae were closed endoscopically. The sphenoid sinus cerebrospinal fluid fistula was closed successfully with fibrin glue and Gelfoam. Five cerebrospinal fluid fistulae were closed successfully using fascia, muscle, and Gel-foam. Two cerebrospinal fluid fistulae were treated conservatively, and only 1 stopped. Anatomic and technical aspects related to the occurrence of cerebrospinal fluid fistulae are discussed. Management and treatment of cerebrospinal fluid fistulae occurring during and after endoscopic sinus surgery is emphasized. When identified intraoperatively or delayed, cerebrospinal fluid fistulae can be managed successfully by endoscopic technique. 