This volume contains papers presented at the IUTAM Symposium on unilateral multibody contacts. Multibody systems very often include phenomena like impacts, stick-slip or time-variant kinematical loops which generate an unsteady behaviour of motion. Each of these unilateral phenomena alone leads to more complexity in analyzing the motion, and the situation becomes worse if such processes take place in multiple contacts of a multibody configuration, especially if these contacts are not decoupled by some force laws, for example. For these cases the complementary properties of contact dynamics and as a consequence the application of complementary algorithms allows the correct and consistent evaluation of the new constraint situation after each new contact event and avoids extensive combinational searches. The time-variant structure of such mechanical systems and thus the state-dependent change of the constraint combinations and the equations of motion afford special analytical and numerical treatment. Mathematical aspects can be characterized by linear complementarity problems (LCP) for plane contacts and by nonlinear complementarity problems (NLCP), homotopy or projection methods for spatial contacts. Worldwide, there exists an increasing scientific community dealing with these problems where, especially in Europe, the efforts are concentrated on the mathematical foundation, on applications for multibody dynamics and for FE-problems. This volume will be of interest to researchers and engineers in the field of applied mathematics, physical and mechanical sciences, and engineering.