This paper presents the research conducted during the last years by the Laboratory of Mechanical Engineering on real-time formulations for the dynamics of multi-body systems, a topic of great relevance for the development of new virtual reality applications. The work carried out by our group has been focused on: a) the development of real-time formulations capable of performing very fast calculations of the dynamics of complex rigid-flexible multi-body systems; b) the experimental validation of the motions, deformations and forces obtained through the application of the above-mentioned formulations, so as to verify that reality is being reasonably well imitated; c) the study of the aptitude of such formulations for becoming part of a virtual reality environment, in connection with user-interface devices. In the paper, a real-time formulation developed by the authors is described, along with some examples of rigid-flexible multi-body systems simulated with such formulation. Moreover, results of the experimental validation of one of the examples are shown. Finally, a simulator based on the proposed formulation is presented.