The nitration of N, N′-disubstituted hydrazines (RNH–NHR) by means of nitric acid – acetic anhydride mixtures has been found to yield, in most cases, the azo derivatives (RN = NR). For example, when R = CH3, (CH3)2(CN)C, CH3CO, or C2H5OCO, azo derivatives were formed. When R = HCO, nitrogen, carbon dioxide, and nitrogen oxides were evolved. An exception was observed with N, N′-dibenzoylhydrazine which, under the same conditions, yielded the N, N′-dinitro-N, N′-dibenzoylhydrazine.