The temperature distribution in an azimuthally symmetric chemical-vapor-deposition reactor is calculated at two pressure regimes. Taken into account is the influence of a silicon wafer situated above a uniformly heated susceptor. In the low-pressure regime, where the mean free path in the gas phase is much greater than the separation between the wafer and susceptor, the wafer is heated solely by radiation. The temperature at the wafer surface can be —20% lower than the susceptor temperature and the temperature drop is nearly independent of the thermal conductivity of the surrounding gas. In the high-pressure regime, where continuum flow exists between the susceptor and the wafer, the later is heated by conduction, convection, and radiation. The temperature at the wafer surface can be —10% lower than that of the susceptor and the temperature drop is strongly influenced by the distance separating the wafer and the susceptor, and by the thermal conductivity of the gas. In both pressure regimes, nonuniform temperature profiles develop at the wafer surface and in the gas phase directly above the wafer. In the reactor geometry studied, a nonuniform susceptor temperature profile would be required to produce uniform wafer and gas-phase temperature profiles. © 1992, American Vacuum Society. All rights reserved.