Irradiance and actinic flux are important parameters that characterize atmospheric radiation. While irradiance is a measure of the energy flux of photons into the atmosphere the actinic flux is the spherically integrated photon flux at any point in the atmosphere. Actinic flux, not irradiance, is required to calculate photolysis rate parameters for air quality simulations. Typically flat plate radiometers are used to measure irradiance but it is often difficult and inaccurate to estimate actinic flux from these irradiance measurements. The use of spectralradiometers equipped with integrating hemispherical collectors to make measurements of actinic flux for clear sky conditions was tested at the Desert Research Institute’s Storm Peak Laboratory in Colorado. The measured irradiance and the derived actinic flux were compared to calculations made with the Madronich model. The modeled irradiance and actinic flux had similar temporal patterns compared to measured values but there are significant differences that may be attributed to model attributes and instrument calibration.