A numerical study of mixed convection from a trapezoidal cavity is carried out. Two openings are adjusted on the plates of the cavity. The inlet opening is horizontal or vertical, while the outlet one is placed horizontally on the bottom wall. The Navier-Stokes equations are solved using a control volume method and the SIMPLEC algorithm is used for the treatment of pressure-velocity coupling. Special emphasis is given to detail the effect of the Reynolds number on the heat transfer generated by mixed convection. The results are given for the parameters of control as, Rayleigh number (Ra = 10(5)), Prandtl number (Pr = 0.72), the inlet and outlet opening width are respectively (C-1 = 0.38 and C-2 = 0.25), the inclination of the tilted wall (0 = 22 degrees) and Reynolds number (10 <= Re <= 1000). The results show that the flow structure and the heat transfer depends significantly on the inlet opening site. Two principal kinds of the problem solution are raised. (C) 2008 Elsevier Ltd. All rights reserved.