This book contains the written contributions to the International Symposium on th Medical Simulation (ISMS’04) held in Cambridge, Massachusetts, USA on June 17 th and June 18 , 2004. Manuscripts are organized around five thematic sections relating to the multidisciplinary field of Medical Simulation: Soft Tissue Properties and Modeling, Haptic Rendering, Real-Time Deformable Models, Anatomical Modeling, and Development Frameworks. The objectives of the symposium are to gather researchers to present their most recent, and promising work, to highlight research trends and foster dialogue and debates among participants. Live demonstrations are also included at the meeting, but cannot be included in this volume. Finally, to address questions about areas for improvement and future directions of the field, we organized a panel of experts including technical, medical and educational representatives. This event continues the successful symposium organized by Herve Delingette and Nicholas Ayache, in France in June 2003. At that meeting we agreed that it would be beneficial for the community to have an annual gathering for the medical simulation community where researchers can exchange ideas and share their work in this emerging field. ISMS’04 is co-organized by CIMIT / Harvard Medical School and Rutgers University.