Deep brain stimulation (DBS) obtains good control of advanced PD symptoms. Chronic stimulation of Stn may alleviate rigidity, dyskinesia and tremor. Anatomical and functional intraoperative mapping are mandatory to obtain careful target localisation. Per-operative macrostimulation was carried out in 22 patients undergoing bilateral DBS in Stn; a volume 6 mm above to 4 mm below Stn was explored. Positive, collateral and adverse effects were recorded every 2 mm. Results obtained during acute stimulation were correlated to anatomical data from stereotactic atlases. Our findings suggest a volume, encompassing the zona incerta, Forel's fields and the lowermost part of anterior thalamus, functionally homogeneous to Stn. In fact, the stimulation of this volume obtains reduction of PD symptoms comparable to Stn.