In this paper we consider the problem of unsteady, laminar, boundary layer flow of a viscous, incompressible, electrically conducting fluid along a semi-infinite vertical plate in the presence of a porous medium with radiation and chemical reactions. Using perturbation techniques the expressions for the velocity distribution, temperature distribution, concentration distribution, shear stress, Nusselt number, and Sherwood number are obtained. The velocity increases with an increase in K, Gr, and Gm.