p-Nitro- and p-nitrosoaniline (III and IV) are the main products of p-azidoaniline (I) photolysis in the presence of oxygen in aprotic solvents, and in CO2 and xenon liquefied at high pressure. In non-polar solvents the formation of III prevails; in solvents with high polarity or polarizability, the formation of IV prevails. Investigations by the methods of stationary low temperature and flash photolysis have shown that p-aminophenylnitrene resulting in a triplet state (II) from the primary processes reacts with oxygen, yielding p-aminophenylnitroso oxide (V). The rate constant of this reaction at 285 K is (8 ± 2) × 106 M−1 s−1 in toluene and (4.5 ± 1.2) × 106 M−1 s−1 in hexane. Further, V undergoes dimerization producing dimeric p-nitrosoaniline peroxide (VI). The rate constant of dimerization of 285 K is (1.4 ± 0.4) × 109 M−1 s−1 in toluene and (0.7 ± 0.2) × 1010 M−1 s−1 in hexane. The dimeric peroxide (VI) decomposing in two channels yields either two molecules of III or two molecules of IV and one molecule of O2.The spectral characteristics of the intermediates (II, V and VI) of p-azidoaniline photolysis in the presence of O2 are determined. The low temperature photochemical reactions of cis-trans isomerization of V and its phototransformation into the final products of III and IV are found to occur. Irradiation of dimeric peroxide VI also leads to the formation of III and IV.