Minimal invasive navigational resection of anosteoma of the lateral pterygoid process via anintraoral approachMinimal invasive tumor surgery needs detailed andexact planning using CT scans to show extensionof the tumor and point out vital structures.Computer assisted surgery allows preoperativeplanning and simulation, intraoperativenavigation and postoperative control. On the baseof an axial spiral CT or MRI data set in ourclinic the STN-Navigation-System (Stryker-Leibinger/Zeiss) is used for preoperative planning and intraoperative controlling of guided biopsies and tumor resection. Minimal invasive resection of an osteoma of the right lateral pterygoid process was performed through an intraoral approach. With a guided drill a two millimeter mini screw could be inserted safely into the osteoma onto which a wire was fixed. After guiding the chisel to the desired point of the external lamina of the pterygoid process the tumor could be completely removed. Intraoperative navigation wih non-invasive registration allows guided biopsies and tumor resections achieving minimal invasive diagnostic and therapeutic treatment in oral and maxillofacial surgery. Keywords: computer assisted surgery, frameless stereotaxy, maxillofacial surgery, tumor surgery