Surgical navigation systems (frameless stereotaxy) have been used in addition to or instead of fluoroscopy during transsphenoidal surgery. This study compares the intraoperative localization by an optical tracking system (Elekta Viewscope) with fluoroscopy. Viewscope and fluoroscope sagittal images were compared by the establishment of a Cartesian coordinate system based on anatomical landmarks and by the spatial localization of surgically relevant points for 20 patients. The Viewscope was found to have a total deviation of 3.0 ± 0.6 mm (mean ± SD) compared to fluoroscopy (p < 0.01). Much of the error resulted from the registration process, which according to the Viewscope software had an expected error of 3.1 ± 0.8 mm for this series of patients, and from the probe-to-system correlation (error of 1.0 ± 0.3 mm). Although frameless stereotactic systems give the surgeon useful trajectory data with three-dimensional visualizations, they remain somewhat inaccurate. The multiplanar abilities of the Viewscope provide an additional but not mandatory advantage to the simplicity and accuracy of fluoroscopy during this type of surgery.