The papers of this book are based on a Symposium on Numerical Simulation in Oil Recovery held at the Institute for Mathematics and its Applications. The major research emphasis is on the modeling of fractures, heterogeneities, viscous fingering, and diffusion-dispersion effects in the flow in porous media. This volume contains seventeen comprehensive papers on the latest developments in this exciting subject. Its diverse presentation brings together the various disciplines of applied mathematics, chemical engineering, physics and hydrology.