Heat transfer associated with the forced convection flow over a conducting slab sited in an aligned uniform stream is investigated analytically and numerically. Both internal and external thermal conductivities are taken into consideration by means of a conjugate model consisting of the full Navier-Stokes equations for the fluid medium and the energy equations for both the fluid and the slab. The analysis facilitates the investigation of the effects of the Reynolds number (Re), the Prandtl number (Pr), the thermal conductivity ratio (k) between the slab and the fluid medium and the slab,aspect ratio (lambda) on the heat transfer characteristics. For Re much greater than 1, boundary-layer theory is used to derive two methods of solution whose results are compared with the full numerical solutions. (C) 1997 Elsevier Science Ltd.