A numerical study of the steady natural convection heat transfer within an inclined trapezoidal enclosure filled with a fluid-saturated porous medium is presented in this paper. The top cylindrical surface of the enclosure is cooled and the bottom cylindrical surface is heated. The remaining two nonparallel plane sidewalls of the enclosure are adiabatic. The Darcy and energy equation tin nondimensional stream function and temperature formulation) are solved numerically using the Alternative Direction Implicit (ADI) finite-difference method. Flow and heat transfer characteristics (stream lines, isotherms and average Nusselt numbers) are investigated for a wide range values of the Rayleigh number, inclined angle and cavity aspect ratio. The present results are compared with those reported by J.P, Caltagirone (J. Fluid Mech. 76 (1976) 337) for natural convection in a porous medium bounded by two concentric horizontal cylinders. It was found that these results are in excellent agreement. (C) 2000 Elsevier Science Ltd. All rights reserved.