An isocentered system for functional stereotactic procedures with the Cosman-Roberts-Wells frame and a CT localizer that allows extrapolation of target data directly from the CT slice is presented. Based on anatomical landmarks and on the scaled corresponding transverse plates of the Schaltenbrand and Wahren atlas, we delineate the thalamic and cerebellar nuclei. Twenty three image-directed functional procedures were performed in one year on 18 patients (7 with Parkinson's disease, 4 with dystonia, 3 persons with essential tremor, 2 patients with choreo-athetosis and 2 with de-afferentiation pain). The 23 procedures included 19 thalamotomies, two dentatotomies and two stereotactic implantations of deep seated brain electrodes. Successful targeting was verified by intra-operative electrical stimulation and postoperative CT scan. Complete reduction of symptoms was observed in 4 persons with Parkinson's disease and in 2 patients with essential tremor with significant improvement observed in the rest of the patients with the exception of the individual with choreo-athetosis. There were no operation-related complications. The reported technique is safer and less distressing for patients than previous radiological procedures and it makes image-directed stereotactic functional neurosurgery available to many units with the CRW frame.