Abstract N-nitroso-N-phenylhydroxylamine, N-nitroso-α-naphthylhydroxylamine, and their sodium salts have been prepared from the ammonium salt of N-nitroso-N-phenylhydroxylamine (cupferron) and the ammonium salt of N-nitroso-α-naphthylhydroxylamine (neocupferron) respectively. The measurements of the UV spectra in solution and the IR spectra with Nujol mull have been carried out on these compounds, including their ammonium salts. The solvent effect and the deuteration effect on the IR spectra have also been examined for the compounds with a hydroxyl group. The formation of a rather strong hydrogen bonding in these aromatic nitrosohydroxyl-amines has been confirmed from the deuteration effect on the IR spectra and from the solvent effect on the UV and IR spectra. These compounds and their salts have shown the absorption band considered to be a chargetransfer band in the UV spectra, and they have also shown the N=O stretching mode between 1450 and 1468 cm−1 corresponding to those of nitrosamines in the IR spectra with the HCB mull.