A numerical study of natural convection between eccentric, horizontal porous cylinders is presented here. The governing equations based on the Darcy - Boussi-nesq assumptions are solved on a very fine grid and for different values of the eccentricity ratio. For moderately high values of the Rayleigh number, there exists an optimum value of the eccentricity ratio for which the total heat transfer is a minimum. The value calculated here for a. radius ratio of 2 and 100 < Ra < 170 (∈ = 0.7) is in good agreement with the one calculated previously by Ban (∈ = 0.6) using a perturbation expansion technique. The very accurate code presented is nevertheless not limited to low or moderate Rayleigh numbers.