['Before operating on 130 patients with pituitary disorders, we evaluated their bone window CT images sliced parallel to the transnasal surgical route to assess the surgical anatomy of the nasal cavity for transnasal surgery.', 'High resolution bone window CT was performed in 3- to 5-mm slices parallel to the imaginary line connecting the inferior margin of the piriform aperture and the top of the sellar floor, parallel to the transnasal surgical route.', 'This CT angle was useful in evaluating the width and depth of the operative field, the bony components of the nasal conchas, deviation of the nasal septum, the bony structure and mucosa in the sphenoid sinus, and the condition of the sellar floor. In patients requiring repeat surgery, the location of thin or thick nasal mucosa, residual bony septum, and inadequate sellar floor opening were easily detected.'] Do usefulness of bone window CT images parallel to the transnasal surgical route for pituitary disorders?