The reactions of hexachlorocyclotriphosphazene, N₃P₃Cl₆, with aromatic primary amines (aniline, p-toluidine, and p-anisidine) yield the derivatives N₃P₃Cl_6–n(NHC₆H₄Y-p)_n[Y = H, Me or OMe, n= 1 or 2 (three isomers); Y = OMe, n= 3 (three isomers), 4 (geminal isomer only), 5, or 6]. The structures of these derivatives and their isomeric compositions have been determined by ³¹P n.m.r. spectroscopy and also by ¹H n.m.r. spectra of the corresponding methoxy and/or dimethylamino derivatives. When diethyl ether, tetrahydrofuran, or MeCN is used as the solvent, non-geminal products predominate at the bis stage of chlorine replacement. However, in the presence of triethylamine, the geminal product is formed exclusively. At the tetrakis stage of chlorine replacement, the geminal isomer is the sole product irrespective of the reaction medium. The reaction of non-gem-N₃P₃CL₃[NHC₆H₄(OMe)-p]₃ with p-anisidine yields only N₃P₃[NHC₆H₄(OMe)-p]₆; formation of non-geminal tetrakis derivatives could not be detected. The mechanistic implications of these results are discussed.