This work group aims at practical user interfaces for 3D imaging data in surgery and medical interventions. The usual monitor based visualization and mouse based interaction with 3D data will not present acceptable solutions. Here we study the use of head mounted displays and advanced interaction techniques as alternative solutions. Different issues such as depth perception in augmented reality environment and optimal data representation for a smooth and efficient integration into the surgical workflow are the focus of our research activities. Furthermore appropriate ways of interaction within the surgical environment are investigated.