An analysis is carried out to study the flow, chemical reaction and mass transfer of a steady laminar boundary layer flow of an electrically conducting fluid of second grade in a porous medium subject to a transverse uniform magnetic field past a semi-infinite impermeable stretching sheet. The governing partial differential equations are converted into ordinary differential equations by a similarity transformation and an analytical solution for this flow is utilized, whereas the concentration profiles are obtained numerically for higher-order reactions. The variations of dimensionless surface concentration and dimensionless surface concentration gradient as well as mass transfer characteristics with various parameters are graphed and tabulated. Our numerical computations show that the effect of destructive chemical reaction is to diminish the concentration boundary layer. This phenomenon is quite the opposite when a generative reaction is present. (c) 2006 Elsevier B.V. All rights reserved.