This book on singular perturbation problems - in particular, stationary reaction-convection-diffusion problems exhibiting layer behaviour - is devoted to the construction and analysis of numerical methods on layer-adapted meshes. A classification and a survey of layer-adapted meshes for various types of boundary-value problems are included. This structured and comprehensive account of current ideas in the numerical analysis for various methods on layer-adapted meshes is addressed to researchers in finite element theory and perturbation problems. Finite differences, finite elements and finite volumes are all covered.