The purpose of incorporating stereotactic methodology into neurosurgical procedures is to consistently achieve a high degree of accuracy and precision in localizing intracranial targets. Therefore, the limits of resolution for the therapeutic intervention itself are a function of the accuracy and precision inherent to the particular stereotactic frame system itself. The total clinically relevant error (application accuracy) comprises errors associated with each procedural step, including imaging, target selection, vector calculation and the mechanical errors of stereotactic frames. To evaluate these parameters, a systematic error analysis was carried out in the 4 most commonly used CT-compatible stereotactic devices: the Brown-Roberts-Wells. Cosman-Roberts-Wells, Kelly-Goerss Compass (modified Todd-Wells) and Leksell frames. Over 7,681 independent test measurements were made. The results suggest a potentially significant degree of error in application accuracy of all stereotactic instrumentation which is accentuated by imaging-associated error. These individual error values must be considered with every clinical use of stereotactic frames.