Regarding to the upcoming techniques in neuroendoscopy the IVth ventricle was examined. First in a series of 30 fresh and fixed anatomical specimens-the vessels injected with LATEX-the fourth ventricle was investigated endoscopically. There are three possibilities to reach the IVth ventricle: coming from the IIIrd ventricle via the aqueductus cerebri, using the basal cisterns through the apertura lateralis Luschkae and coming via the cerebellomedullar cistern through the foramen of Magendi. Using different kinds of endoscopes (rigid, flexible and steerable flexible)-diameter ranging from 5 to 9 french-with different optical systems (0 degree, 5 degrees, 30 degrees, 75 degrees) and different light sources (Halogen, Xenon) the anatomical details seen under the endoscope and the topographical landmarks of the approaches were investigated, presented and discussed. Based on the experience at the end of the cadaver work a short comment on which kind of equipment seems the best was given. A series of 14 clinical cases was presented as the second part of the study (7 cases with a tumor in the IVth ventricle-2 metastasis, 3 gliotic tumors, 1 ependymoma, 1 medulloblastoma, 3 patients with an occluded aqueduct because of meningo-ventriculitis and 4 patients with cystic malformations). The neuroendoscopic approaches, the neuroanatomical details relevant for surgery and the clinical data will be given and discussed. In general no intraoperative or postoperative complications were seen. In conclusion our experience from the theoretical neuroanatomical and the clinical part as well as the advantages and disadvantages from the different kind of endoscopes and approaches are discussed.