In neurosurgery, three-dimensional data from different modalities are registered, segmented and visualised for pre-, intra-and post-operative medical imaging. A combination of the multimodal data sets provides additional information for the analyses of anatomic and functional correlations and for surgical planning. For routine use, it is important to design a software application that is simple and intuitive to use. A neurosurgical operation planning system is realised in combination with novel 3D-interaction and visualisation technologies. The development of additional functions, such as automatic segmentation and elastic registration, enhances the usability of the systems to approach further clinical objectives.