Medical simulators allow a risk-free training or rehearsal of surgical procedures for medical students and experienced surgeons. These simulators often utilize virtual reality hardware, such as special haptic devices to provide feedback and 3D input, as well as stereoscopic rendering on various display systems. Obviously, the simulation and rendering has to rely on high quality 3D models. In this presentation we want to demonstrate how Blender can be used as a powerful tool in the development of medical simulators. In a case study, we provide insight into the development of a human heart surgery simulator and how Blender has been utilized in this process. The workflow from medical imaging CT and MRI datasets, the modeling steps in Blender, the export and the integration into the simulator will be described.