The limits of the area to be destroyed during the stereotaxic surgery for the treatment of tremors are described taking into account the complications due to lesions erroneously performed. The method applied is commented in order to control the accuracy of the target delimitation, describing the technique employed in 23 thalamotomies, recording the electrical activity of the thalamic nuclei acrossed and researching evoked potentials thanks to the somatotopic tactil representation in the ventral posterior nuclei. The method permits to reduce radiologic errors giving more accuracy for the delimitation of thalamic target in the three planes of space.