Azomethane has been photolyzed in the presence of CH3CHO and CH3CDO, and the results compared with the direct photolysis of the aldehydes. The activation energies found were 6.8 and 7.8 kcal./mole, respectively, for the reactionsThe results furnish evidence that only an acyl hydrogen is captured. Evidence has also been found for the occurrence of wall reactions and the disproportionation reaction