MHD flow of a viscous conducting fluid past a stretched vertical permeable surface with heat source/sink and chemical reaction has been analysed. Constitutive equations for velocity, temperature and concentration have been formulated and solved with specific boundary conditions. Variation of velocity, temperature and concentration have been shown by graphs. The values of skin-friction, rate of heat transfer and concentration gradient have been entered in the tables for various values of fluid parameters like Grashof number, Prandtl number, Schmidt number, Hartmann number, Eckert number, source/sink parameter, permeability parameter and chemical reaction parameter. It is observed that the flow, heat and mass transfer are influenced by the external transverse magnetic field and porosity of the medium. Actually the imposed magnetic field decelerates the flow. The presence of sink reduces the temperature and the source increases the temperature of the fluid which is practically a case. Concentration decreases with the increase of Schmidt number.