The intraoperative orientation of a surgeon during video- endoscopic endonasal procedures is a challenge. Individual anatomical knowledge and modern 3D-computer assisted navigation technologies provide a maximum of information during surgery (=patient safety). A such, the position of a tool is visualized in the preoperative radiologic images as the center of cross-hairs in typical axial, coronal and sagittal views of, e.g. a stack of CT images. We have implement the augmentation of reality by superimposing the positional data and additional guiding structures- access paths and delicate structures- to the live video of the surgical site. The currently available telecommunication infrastructure allows to connect any two locations in order to facilitate and allow remotely proctored preoperative planning, consultation and guidance. This allows to provide the maximum of intra-operative information, with an expert advice from a remote specialist. We have been achieving satisfactory results on base of telephone, ISDN, Ethernet and Atm connections and could demonstrate that the ARTMA technology provides essential information for a remote expert, who shares the same information as the local surgeon, and can be an essential aid for difficult surgical interventions. The ARTMA Knowledge Guided Surgery can become an important tool for further optimizing surgery.