Thirty-five consecutive patients with the clinical diagnosis of fenestral otosclerosis were evaluated with high-resolution computed tomography (CT). Twenty-six were diagnosed as having this disorder by CT evidence of abnormal bony excrescences at or adjacent to the oval window. The diagnosis was made upon examination of 1.5-mm-thick targeted sections obtained at 0.5-mm intervals in the axial projection. Coronal sections were also included. Sections were also evaluated for evidence of plaque formation elsewhere in the lateral wall of the labyrinth and for surgical obstacles such as an abnormally wide cochlear aqueduct, a high jugular vein, and a dehiscent facial nerve. It is concluded that fenestral otosclerosis may be accurately diagnosed with proper CT techniques.