Background and study aims: To investigate targeting of the Nucleus subthalamicus (STN) for implantation of deep brain stimulation (DBS) electrodes in patients with advanced Parkinson’s disease. The aim of this study was to evaluate the accuracy of the individually planned target by T2-weighted MRI compared to the previously used standard coordinates, to evaluate the efficacy of intraoperative microelectrode recording, especially by using only one central trajectory and to evaluate the success of the operation concerning the reduction of symptoms and side effects. Patients, material and methods: 52 patients, who underwent DBS between 2003 and 2006 in the Neurosurgical Department at the University Hospital Marburg, were endosed in the study. Targeting of the STN was done by fusion of MRI and CT-scans prior to the operation. During operation, microelectrode recording of the central trajectory was conducted routinely. In case of failure in recording the signal characteri- stic of the STN, microelectrode recording was done with one additional out of five possible trajectories. A test stimulation was performed intraoperatively in the awake patient. We evaluated a one year follow-up of the motor examina- tion (UPDRS III) and the stimulation induced or the operation-dependent side effects. Results: We found the laterality of the target point to be significantly lower (11,09/ - 11,17mm) than the previously used standard coordinates (12/ -12mm). Nonetheless the central trajectory led to microelectrode recording of the STN signal in 74% for the left and 68% for the right side. Additional microelectrode recordings of other trajectories after failed central recording showed an additional benefit only in solitary cases. The angle of the trajectory had no systematic influence on side effects during test stimulation and on the postoperatively reported psychopathological outcome. There was a significant benefit documented by the UPDRS motor score without medication from pre- to postoperative (symptom reduction on average by 34,3 points). Conclusion: The planning of STN target on MRI more medial and dorsal than previously performed was accurate and led to good results of intraoperative microelectrode recording with the central trajectory. Hereby, the permanent stimulation electrode with four contacts placed with the top of the last contact on the target point, covers the whole STN. The effectiveness is supported by the the positive motor outcome in one year follow-up. Microelectrode recording of the central trajectory is sufficient to confirm the STN target and especially relevant to indicate misplacement. This happens due to the effect of the socalled ”brain shift”. The use of only one trajectory compared to five parallel channels results in a reduction in operation time and the risk of intraoperative complications. In our patient collective, there was no relation between the angle of the trajectory and the outcome of the operation or any side effects. Further controlled studies are needed to investigate these multiple interactions of deep brain stimulation for Parkinson’s disease.