We are currently involved in an open-source, real-time simulation plateform project. The SOFA project is the result of a collaboration between the CIMIT Simulation group (Harvard Medical school, leader Stephane Cotin), and INRIA projects EVASION (leader Marie-Paule Cani, INRIA Rhônes-Alpes) and ASCLEPIOS (leader Nicolas Ayache, Sophia-antipolis). This project was born when it appeared CIMIT and ALCOVE project, separately, had started quite the same work: propose a framework flexible enough so that people would reuse algorithmic blocks, and change, for a given object, collision representation, visual and mechanic representation, as independently as possible. We chose to join effort, and after EVASION and ASCLEPIOS joined us in this work, INRIA supported this project by providing 2 engineers, for 2 years, for this project. The alpha version of the SOFA plateform should be made public soon. It provides multi-threaded support for simulation algorithmic (not only for drawing and/or haptic control), proper handling of group (for collision and constraints), and software structure that provides enough flexibility and genericity for people to consider functional blocks as exchangeable, and semantically start to build their own simulator efficiently.