A prototype stereotactic head frame has been constructed for use in conjunction with a computed tomographic (CT) body scanner. Interactive software has been developed to allow target delineation using a standard CT scanner computer and image display console. The mathematic equations fundamental to this software are described. In preliminary experiments, it has been demonstrated that this frame can accurately direct a probe to an appropriately delineated target in a series of CT scans. A theoretic method for determining accuracy is presented; results suggest that this system represents a significant improvement over classic methods of neurosurgical stereotactic localization.