Studying the clinical effects induced by electrical stimulation of the subthalamic nucleus (STN) area in a parkinsonian patient under local anesthesia is a mandatory step to determine the precise location of the final chronic electrode. Using multiple microelectrodes, preferably in a concentric parallel array allows a precise mapping of the STN region. The most reliable features to determine the suitable target are stimulation-induced dyskinesias and rigidity decrease at a low intensity without adverse effects or only at far higher intensities. New skills are needed to assess all stimulation-induced effects and interpret them in anatomo-functional terms.