The symposium was organized with the intention of creating an opportunity for mathematicians and engineers working on nonlinear problems to communicate with each other and exchange experiences in the use of boundary integral methods. The spirit of the symposium is clearly reflected in the papers collected in the volume. Some mathematical issues of boundary integral methods for the solution of nonlinear problems are examined in depth. In addition, several applications to fluid and solid mechanics and heat transfer problems are presented. The reader is given a wide overview of the broad class of applications where boundary integral methods represent a very appealing tool for the analysis of nonlinear problems.

This volume contains edited papers from IABEM-90, the 1990 Symposium of the Interna tional Association for Boundary Element Methods (IABEM). As stated in the By-Laws of the Association, the purposes of IABEM are: 1. to promote the international exchange of technical information related to the devel opment and application of boundary-integral equation (BIE) formulations and their numerical implementation to problems in engineering and science, commonly referred to as the boundary element method (BEM); 2. to promote research and development activities for the advancement of boundary integral equation methods and boundary element solution algorithms; 3. to foster closer personal relationships within the BEM community of researchers. The objectives of the Symposium, in line with those of the Association, was to provide a forum where the two "souls" of the Association, i. e., (i) mathematical foundations and numerical aspects, and (ii) engineering applications could be integrated. We believe that the first aspect has been neglected in too many of the BEM Symposia held in the past, which, with a few exceptions (notably, the IUTAM Symposia on the subject) have emphasized the practical aspects of the method. As a consequence, we have tried to give a stronger emphasis to the more theoretical issues: this is attested for instance, by the fact that the two general lectures were given by Prof. Gaetano Fichera, of the University of Rome "La Sapienza," and Prof."

This volume contains the Proceedings of the IABEM International Sym- posium on Boundary I~ntegrall Methods for Nonlinear Problems, held at the Certosa di Pontignano near Siena (Italy) on May 28 - June 3, 1995. The Symposium was sponsored by IABEM (International Association for Boundary Element Methods) and co-sponsored by IUTAM (International Union of Theoretical and Applied Mechanics). The members of the Scientific Committee of the Symposium are Heinz Antes (Germany) Satya N. Atluri (USA) Dimitri E. Beskos (Greece) Thomas Cruse (USA) Massimo Guiggiani (Italy) George C. Hsiao (USA) Shoichi Kobayashi (Japan) Gunther Kuhn (Germany) Vladimir G. Maz'ya (Sweden) Luigi Morino (Italy, co-organizer) Renzo Piva (Italy) Wolfgang L. Wendland (Germany, co-organizer) Pieter J. Zandbergen (The Netherlands) Franz Ziegler ( Austria, IUTAM representative) The contributions include mathematical issues on boundary integral equa- tions and boundary element methods as well as applications to fluid and solid mechanics and to heat transfer. The individual contributions are briefly reviewed in the following.