This book contains original papers presented at the Fourth International Conference on Hyperbolic Problems which was held on April 3-8, 1992 in Taormina (Sicily), Italy. The aim of the Conferences in this cycle is to bring together scientists with interest in theo retical, applied and computational aspects of hyperbolic partial differential equations. The contributions, well balanced among these three aspects, deal with: mathematical theory of wave propagation, kinetic theory, existence, uniqueness and stabil ity of solutions, mathematical modeling of physical phenomena, stability and convergence of numerical schemes, multidimensional computational applications, etc. The papers are printed in the authors' alphabetic order following the idea both of mixing together topics of interest to different areas and of considering either theoretical results connected with applied problems or new applications with an essential mathemat ical approach. The Proceedings from the previous Conferences held in St. Etienne (1986), Aachen (1988) and Uppsala (1990) appeared respectively as: Lecture Notes in Mathematics, 1270, P. Carasso, P. A. Raviart & D. Serre (Eds.), Springer-Verlag (1987) Notes on Numerical Fluid Mechanics, 24, J. Ballmann & R. Jeltsch (Eds.), Vieweg (1989 ) Third International Conference on Hyperbolic Problems, B. Engquist & B. Gustafs son (Eds.), Vol. I, II, Studentlitteratur, Uppsala University (1991). The organizers and the editors of the Conference would like to thank the Scientific Committee for the generous support, for suggesting the invited lectures, and for selecting the contributed papers."