This book deals with some theoretical investigations of unsteady flow of second order visco elastic fluids through a porous medium. This book is broadly divided into 6 chapters, the opening chapter is introductory in nature highlighting mathematical modeling of visco elastic fluids that flow through porous media and states the flow-governing basic equations together with the related boundary conditions. The author's investigations are incorporated in chapters ( II - VI) that follow. In all the investigations, the flow is governed by generalized momentum equations which take into account the shear stresses and the inertia acceleration in addition to the Darcy's resistive force. The effects of the visco elastic nature of the fluid and the porous nature of the medium are expressed in terms of a compounded non-dimensional flow parameter ( ).