The research described in this thesis was carried out in the Computer Graphics & CAD/CAM group at Delft University of Technology. The project was directly supervised by Frits Post. It is the sixth project in a series of PhD projects on data visualization, but the first project concerned with Virtual Reality and data visualization. In summer 1998, the Responsive Workbench facility was installed at the High Performance Applied Computing Center (HPaC) at TU Delft. The Workbench was intended to serve as a high performance visualization system, working in a cluster with the other HPaC supercomputers. This PhD project was initiated to set up an environment for high-performance data visualization, so that our group and other research groups of TU Delft could use this VR facility. Another aspect was to include computational steering facilities, which would enable the user to control a supercomputer simulation directly from the virtual environment displayed on the Workbench. For the purposes of our research we developed the RWB Library and the VRX toolkit, together a basic environment for visualization and interaction on the RWB. The thesis covers three main topics: design and development of VR applications, interaction in virtual environments, and visualization of data, originating from scientific simulations. On various case studies we have demonstrated that the Responsive Workbench concept with our software and techniques can provide an efficient visualization environment with natural spatial interaction. The case studies were done in co-operation with internal TU Delft and external research groups. One of the early applications was an interactive 3D visualization of the flooding risk simulations, provided by WL|Delft Hydraulics. The Molecular Dynamics visualization and computational steering case study has been conducted in close co-operation with the Computational Physics group (Faculty of Applied Sciences, TU Delft). The visualization of atmospheric data, originating from cumulus clouds simulations, has been performed together with the Thermal and Fluids Sciences group (Faculty of Applied Sciences, TU Delft).