The unsteady laminar flow of an incompressible viscous fluid and heat transfer between two parallel porous plates are studied in the presence of a uniform suction and injection considering variable properties. The viscosity and thermal conductivity of the fluid are assumed to vary with temperature. The fluid is subjected to a constant pressure gradient and a uniform suction and injection through the plates which are kept at different but constant temperatures. The effect of the suction and injection, the variable viscosity and thermal conductivity on both the velocity and temperature fields is studied.