This book concerns a rapidly developing area of science that deals with the behavior of porous media saturated by fluids. Three basic aspects of this field are rather uniformly balanced in the book; namely, complex physical mechanisms of processes in porous media, new mathematical models, and numerical methods of process study. The following topics are included: homogenization and up-scaling of flow through heterogeneous media; micro-structural laws of complex flow at the pore scale; flow with phase transition and chemical reactions in porous media; wave propagation in saturated porous media; numerical model of flow in natural oil reservoirs; non-classical models of flow, percolation, fractals, foam flow; multi-phase flow with free surface. The contributors to this volume are leading researchers in the field.