History and Scope The MEDSI workshop started at Swiss Light Source in 2000. The state of the art and outlook were presented on mechanical engineering design of equipments and instrumentation in third generation light sources. It was followed by the second workshop at Advanced Photon Source in 2002 and by the third one at European Synchrotron Radiation Facility in 2004. SPring-8 will host for fourth MEDSI workshop as a satellite meeting of SRI2006, covering the following scopes: Novel designs of accelerator and beamline components High precision positioning mechanisms Vibration and mechanical stability High heat load analysis and design Opto-mechanical devices Insertion devices, front ends and vacuum chambers Modelling and experimental validation aspects MEDSI 2004     May 24-27, 2004     ESRF, Grenoble, France MEDSI 2004 program MEDSI 2002     September 5-6, 2002     Argonne, Illinois USA MEDSI 2002 program MEDSI 2000     July 13-14, 2000     Paul Scherrer Institute, Cilligen PSI, Switzerland