On March 14-18, 1983 a workshop on "Chemical Instabilities: Applications in Chemistry, Engineering, Geology, and Materials Science" was held in Austin, Texas, U.S.A. It was organized jointly by the University of Texas at Austin and the Universite Libre de Bruxelles and sponsored qy NATO, NSF, the University of Texas at Austin, the International Solvay Institutes and the Ex xon Corporation. The present Volume includes most of the material of the in vited lectures delivered in the workshop as well as material from some posters, whose content was directly related to the themes of the invited lectures. In ,recent years, problems related to the stability and the nonlinear dynamics of nonequilibrium systems invaded a great num ber of fields ranging from abstract mathematics to biology. One of the most striking aspects of this development is that subjects reputed to be "classical" and "well-established" like chemistry, turned out to give rise to a rich variety of phenomena leading to multiple steady states and hysteresis, oscillatory behavior in time, spatial patterns, or propagating wave fronts. The primary objective of the workshop was to bring together researchers actively engaged in fields in which instabilities and nonlinear phenomena similar to those observed in chemistry are of current and primary concern : chemical engineering (especially surface catalysis), combustion (dynamics of ignition, flame sta bili t;y), interfaces (emulsification, dendritic growth), geology (regularly repeated patterns of mineralization 1n a variety of spabe scales), and materials science (dynamical solidification, behavior of matter under irradiation).