A study is made of natural convection in a horizontal annular porous layer in rotation about its axis. Isothermal boundary conditions are applied on both inner and outer boundaries, with the outer boundary being warmer. For such conditions, no symmetry with respect to a vertical diameter can be expected for the flow and temperature fields and the whole annular region must be considered. Two-dimensional steady state solutions are obtained numerically. Results indicate that the rotation generates a net circulating flow around the annulus relative to the porous matrix and drastically reduces the overall heat transfer. These effects occur at relatively low angular velocities for which the centrifugal forces are negligible compared to gravity, and inertial effects may be neglected.