Eighty-three consecutive functional stereotactic procedures (56 thalamotomies, 1 medial thalamotomy, and 26 chronic brain stimulatory electrode introductions) were done using CT to identify the three-dimensional coordinates of anterior and posterior commissures. The three-dimensional locations of the tactile relay in ventrobasal complex for manual digits were then determined as the first step in physiological corroboration of target site using single-cell recordings and microstimulation. The measured location of this structure was then compared with that predicted by the Schaltenbrand and Bailey atlas. There was no discrepancy in the mediolateral plane in 62.7%, in the dorsoventral plane in 63.9%, and in the anteroposterior plane in 44.6% of the cases. Over 2 mm deviation occurred in 10.8, 12.0, and 19.2% of the cases in these three planes, respectively. This precision of localization is better than that reported with ventriculography. Many of the larger discrepancies occurred in patients who had suffered from stroke, multiple sclerosis, severe head injury, or after craniotomy.