Films of two air-blown asphalts were exposed to the carbon arc at different intensities to determine the effect of radiant energy intensity on the rate of asphalt oxidation. The oxidation rates were established by measuring the changes in infrared absorption in the carbonyl band as a function of exposure time. The intensity of the radiant energy was varied by the voltage adjustment switch on the accelerated weathering machine or by moving the samples closer to the arc. The intensity was monitored by power consumption and the incident flux by chemical dosimetry. It was found that: (1) the asphalt oxidation rate increased with the intensity of the carbon arc; (2) the radiant energy output of the accelerated weathering machine tends to level off at the higher voltage settings; and (3) at the maximum voltage setting of the accelerated weathering machine, the incident radiant flux does not equal or exceed that which can be absorbed by asphalt. Monitoring the incident radiant energy is recommended as a part of the accelerated weathering procedure for asphalt.