New techniques for preoperative risk assessment in liver surgery are presented in this work. Thereby, the determination of safety margins around tumors is addressed which is a challenging task for surgeons. Besides a method to define safety margins with uniform width, a method to define non-uniform safety margins is proposed while considering robustness and sensitivity of vascular risk. In addition, techniques for intraoperative support of liver interventions are introduced. First, the intraoperative adaptation of surgical planning data is focused. Second, new visualization techniques, i.e. surgical risk maps and an approach for illustrative augmented reality are presented. The developed visualization techniques provide a new and objective basis for the assessment of risks during liver surgery. Third, new techniques for auditory support for navigated liver surgery are introduced.