The Sixth Workshop on Optimization and Numerical Analysis was held in Oaxaca, Mexico, in January 1992. The participation of many of the leading figures in the field resulted in this excellent state of the art volume on continuous optimization. The papers presented here give a good overview of several topics including interior point and simplex methods for linear programming problems, new methods for nonlinear programming, results in non-convex linear complementarity problems and non-smooth optimization. There are several articles dealing with the numerical solution of diffusion--advection equations. For researchers and postgraduate students in optimization, partial differential equations and modelling.