Numerical solutions of the Navier-Stokes and energy equations have been obtained to predict the fluid flow, temperature profiles, and heat transfer in a rotating disk reactor. The effects of buoyancy, variable properties, and finite geometry have been included for helium. It is shown that recirculation of the gas can be reduced or eliminated by increasing the uniform velocity at the inlet of the reactor above the asymptotic value for a one-dimensional, variable-properties, infinite rotating disk. This is true for both adiabatic and isothermal reactor walls.