Fluid-structure interactions (FSI), that is interactions of some movable or deformable structure with an internal or surrounding fluid flow, are among the most important and, with respect to both modelling and computational issues, the most challenging multi-physics problems. The variety of FSI occurrences is abundant and ranges from tent-roofs to micropumps, from parachutes via airbags to blood flow in arteries. This volume of LNCSE contains a collection of papers presented at the International Workshop on FSI held in October 2005 in Hohenwart and organized by DFG s Research Unit 493 FSI: Modelling, Simulation, and Optimization . The papers address partitioned and monolithic coupling approaches, methodical issues and applications, and discuss FSI from the mathematical, informatical, and engineering point of view.