Transtympanic endoscopy provides a unique opportunity to view the undisturbed contents of the middle ear. Fiberoptic and rigid endoscopes have been used for thorough examination of the middle ear without the need for local anesthetics or surgical trauma. Endoscopy is now routinely used in the evaluation of a perilymphatic fistula and the patient is awake during an intermittent forceful Valsalva maneuver. Oval and round windows in both ears of five cats were studied endoscopically to evaluate surgically created fistulas. Excellent visualization of the defect was obtained in all instances. Endoscopy is a useful office technique for the evaluation of perilymphatic fistula. It reduces the need for surgical exploration and provides a satisfactory examination of the middle ear. Obliteration of the window niche can even be performed through the myringotomy using autologous blood.