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Surgical ablation is a well-accepted treatment for liver malignancies due to its ability to preserve the surrounding healthy liver tissue as opposed to surgical resection. Precise intraoperative localization of the lesion and correct needle placement are crucial factors for complete tumor ablation. These are difficult tasks due to interpatient variability and technical limitations of current technologies. Surgical navigation provides a live virtual representation of the surgery by showing the position of surgical instruments with respect to the critical anatomy. Navigation can improve tumor localization during surgical resection and it is therefore expected to similarly improve tumor ablation. The development and the clinical implementation of surgical navigation for hepatic tumor ablation were therefore explored in this thesis. A sterilizable adapter was developed carrying an electromagnetic (EM) sensor. This adapter is attachable to the ablation needle in order to track the surgical instrument. The tracking accuracy for this adapter calculated with respect to an EM tracked calibrated block was comparable to the Aurora 6DOF probe, a pointer currently used in the standard workflow of surgical navigations. With the use of this adapter, a virtual representation of the ablation needle could be presented to the surgical team. The workflow for navigated liver ablation was tested intraoperatively by three hepatobiliary surgeons. A cross-hair (i.e., bullseye) view was preferred by the surgeons to guide the ablation needle to the center of the target lesion. In this view, the tumor was visualized as if looking through the tip of the ablation needle. With the system usability score (SUS) of 65, refinement of the software visualization was indicated. Nonetheless, the surgeons want to use the system frequently and responded that it aided in localizing tumor(s), reducing complications, obtaining negative ablation margins and increasing certainty in decisions and actions. Next, Technical Medicine