An analytical study of free convection flow near an impulsively started infinite vertical plate with Newtonian heating in the presence of thermal radiation and constant mass diffusion was performed. The mathematical model reduced to a system of coupled linear partial differential equations for the velocity, the temperature, and the concentration; the closed-form exact solutions were obtained by the Laplace transform method. Representative velocity and temperature profiles were graphed and the numerical values of the skin friction and the Nusselt number were calculated. The effects of different system parameters, such as the radiation parameter, buoyancy ratio, Grashof number, Prandtl number, Schmidt number and time on the velocity, temperature, skin friction, and Nusselt number, were examined in detail. It was observed that the velocity increased for aiding flows, whereas it decreased for opposing flows. The velocity decreased with increasing Schmidt number and radiation parameter. The skin friction decreased in the presence of aiding flows whereas it increased in the presence of opposing flows. Furthermore, the skin friction increased with increasing Schmidt number and radiation parameter. © T�BİTAK.