We present a set of partitioning tools that classify a tetrahedral mesh into different regions of interest while preserving mesh consistency. These regions can then be individually visualized, repositioned, or combined for further analysis or processing. A partitioning operation, either defined analytically (by a formula) or geometrically (by a surface mesh), is applied globally to the model. A hierarchical data structure is used to store region information and consecutive partitioning operations: it ensures consistency between the specified regions of the volumetric mesh and the visualized surface mesh. Similar to volumetric cutting, subdivision is used to split the initial model into regions. Subdivision of tetrahedra that contain multiple intersection points per edge is a non-trivial task. An extension to existing subdivision methods is presented which handles the subdivision of such tetrahedra in an iterative way. Since the partitioning of a volumetric mesh is an important task in surgical planning, this paper finally shows that the presented algorithms can be successfully integrated in a virtual reality planning system.