The present paper reports numerical results of mixed convection and surface radiation within a horizontal ventilated cavity heated from below and provided with an adiabatic thin partition on the heated surface. Air, a radiatively transparent medium, is considered to be the cooling fluid. The effect of the governing parameters, which are the Reynolds number, 200 Re 5000, the relative height of the baffle, 0 Hb 0.75, and the emissivity of the walls, 0 1, on the fluid flow and heat transfer characteristics is studied in detail. The maximum and mean temperatures, the ratio, QE/QL, of the heat quantities leaving the cavity through the exit, QE, and through the left vertical cold side, QL, are also presented versus the above controlling parameters.