It is common in epilepsy surgery to implant grids and strips of electrodes between the skull and brain or inside the brain, in order to localize functional areas. MR scans are currently used for a variety of image-guided surgical planning tasks, including the localization of the electrode grids. However, the MR scan taken of a patient with implanted electrodes is distorted, and it is difficult to visualize and relate the electrode positions to head and brain structures. For this reason we have developed an automatic algorithm that reliably extracts grids of electrodes from corrupted post-op MR scans. The grid is fitted as a smooth, curved surface through the estimated electrode positions, properly estimating the orientation of the thin disk-shaped electrodes. The extracted grid is then displayed in 3D together with the desired brain structures, coloring the electrodes corresponding to particular functional areas. It is now much easier to visualize and locate the positions of the important functional areas with respect to other brain structures and plan the surgery. This method is currently in clinical use within the Department of Neurosurgery, Yale University and Yale New Haven Hospital.