The goal of this study was to investigate the relationship between the peoperatite audiometric levels and CT findings. and the pathological 4:hrlitges observed during stapes surgery. Thirty consecutive patients with clinical diagnosts of fenestral otos-clawasis were evaluated with High-resolution computed tomography (CT) ad carbological tests. Twenty-six were diagnosed as having this disor-der bg CT evidence of abnormal bony excrescence at the oval window. The chagrin& was made upon examination of 1 mm thick targeted sec-ciSexined at 1-mm intervals In the semi-axial with 25° offonvard tilt-iypaperkn. Coronal section were also included. A &sea relationship was found between the size of the fenestral focus aid the air-bane gap. However, the degree and extent of bony footplate sigtosis could not be reliably predicted by the size of the air-bone. gap. Introduction Ada,* otosderosis was de-moted bistopathologically nearly Jess ago, its diagnosis is. to day. made clinically (Nau-man er.. al_ 2005). The diagnosis based on history. absence of Wale middle ear changes on ot-exammation and audio-tidings of conductive or Mind bearing loss associated with an absent stapedial reflex. It is will recognized that non of these factors will accurately pre-dict the pattern and extent of pathological change present in the oval window in a given case (Shea et. al.. 2003). Technical developments in body section radiography have