The effects of buoyancy-induced streamwise pressure gradients on laminar forced convective flow and heat transfer over a horizontal flat plate are studied analytically by the local similarity and local nonsimilarity methods of solution. Numerical results for the local surface heat transfer, wall shear stress, and velocity and temperature distributions are presented for gases having a Prandtl number of 0.7. It is found that both the local Nusselt number and the friction factor increase with increasing buoyancy forces for aiding flow and decrease with increasing buoyancy forces for opposing flow. With regard to the heat transfer results, significant buoyancy effects were encountered for Grx/Rex5/2 > 0.05 and < −0.03, respectively, for aiding and opposing flows. The buoyancy-affected velocity profiles for the aiding-flow case exhibited an overshoot beyond the free stream velocity. Results from previously reported series solutions and from an integral momentum/energy solution were found to be accurate only when the buoyancy effects are small. The present study provides results for intermediate range buoyancy force effects, which have not been reported previously.