A first intercomparison of J sub(N) sub(O) sub(2) measurements by actinic flux spectroradiometry (SR) and chemical actinometry (CA) was performed in summer 1997 in Julich, Germany. During this experiment (JCOM97) a large set of data was collected with a time resolution of similar to 1 min, showing a high linear correlation (R = 0.998) in J sub(N) sub(O) sub(2) . Linear regression indicates a good absolute agreement with the CA being 6% higher than SR if the quantum yield recommended by NASA/JPL (1997) and recently published data of the NO sub(2) absorption spectrum ( sigma sub(N) sub(O) sub(2) ) is used for the evaluation of the SR-data. The influence of using previously published sigma sub(N) sub(O) sub(2) data is discussed. Overall the comparison suggests that J sub(N) sub(O) sub(2) can be measured by either CA or SR with an accuracy of better than 10%.