In the past decade computer models have become very popular in the field of biomechanics due to exponentially increasing computer power. Biomechanical computer models can roughly be subdivided into two groups: multi-body models and numerical models. The theoretical aspects of both modelling strategies will be introduced. However, the focus of this chapter lies on demonstrating the power and versatility of computer models in the field of biomechanics by presenting sophisticated finite element models of human body parts. Special attention is paid to explain the setup of individual models using medical scan data. In order to reach the goal of individualising the model a chain of tools including medical imaging, image acquisition and processing, mesh generation, material modelling and finite element simulation –possibly on parallel computer architecturesbecomes necessary. The basic concepts of these tools are described and application results are presented. The chapter ends with a short outlook into the future of computer biomechanics. The field of biomechanics suffers from one very severe restriction; in general it is not possible for ethical reasons to measure forces and pressure inside the human body. Thus, typical measurement technology in biomechanics works on the interface between body and environment. Force platforms dynamically quantify reaction forces when a person is walking or running across the sensor, electromyography (EMG) monitors action potentials of contracting muscles with electrodes attached to the human skin. The information provided by the measurement technology is very important to investigate the mechanics of movements, but is not sufficient to answer questions like: • How can we optimise movements (e.g. in sports or rehabilitation) in order to minimise the loads on the joints? How can we better understand mechanisms of injury and thus improve prevention? These questions are related to the human body. • How do we have to design the equipment to optimally suit the patient’s or the athlete’s requirements in terms of mechanical behaviour? These questions are related to the medical or technical equipment. This optimisation process has three aspects: • Ineffective and destructive loading has to be minimised (e.g. by damping through innovative cushions in the shoe sole or improved orthotic devices). • Body protection has to be maximised (e.g. through better design of cyclists’ helmets or the interior of automobiles).