This paper reports an analytical and numerical study of natural convection heat and mass transfer through a vertical porous layer subjected to uniform fluxes of heat and mass from the side. The flow is driven by the combined buoyancy effect due to temperature and concentration variations through the porous medium. The first part of the study contains an analytical Oseen-linearized solution for the boundary-layer regime and Le = l,and a similarity solution for heat-transfer-driven flows(n = 0)and Le > 1. The second part of the study contains an extensive series of numerical experiments that validate the analytical results and provide heat and mass transfer data in the domain not covered by analysis. The numerical results cover the Rayleigh number range 20 ≤ Ra ≤ 105, the buoyancy ratio range -11 ≤ n ≤ 9, the geometric aspect ratio range 1 ≤ H/L ≤ 4 and the Lewis number range 0.03 ≤ Le ≤ 40. © 1986.