The attenuation of solar radiation by the atmosphere between the heliostat and receiver of a Central Receiver solar energy system has been computed for a number of atmospheric conditions and tower-heliostat distances. The most important atmospheric variable is found to be the atmospheric aerosol content. No dependence of atmospheric water vapor is found and only a weak dependence on solar zenith angle. For a 500 m heliostat-tower distance two to four percent reductions are expected under typical desert conditions (50 to 120 km visibility). The reduction is approximately linear with heliostat-tower distance. A representative value of the attenuation coefficient is 0.051 km/sup -1/.