Combined effects of natural convection and radiation on a laminar boundary-layer flow over a semi-infinite horizontal flat plate are studied. Increasing the natural convection-radiation interaction in the boundary layer increases the shearing stress on the wall, the boundary-layer thickness, the maximum velocity attainable by fluid, and the buoyancy force in the boundary layer. However, the temperature gradient at the plate decreases with increasing interaction. They generally increase with increasing temperature ratio. Automated computations of the dimensionless velocity, temperature, and buoyancy force in the boundary layer yield convergent solutions which are substantially different from those available in the literature for high natural convection-radiation interactions.