This volume is a collection of papers presented at the IABEM International Symposium on Boundary Integral Methods for Nonlinear Problems, held at Pontignano (Siena, Italy) on May 28-June 3, 1995 and co-sponsored by IUTAM. 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. Within the vast literature on boundary integral methods, this volume is probably the first dedicated specifically to nonlinear aspects. It gives the reader a wide overview of the broad class of applications where boundary integral methods represent a very appealing tool for the analysis of nonlinear problems.