The reactions of hexachlorocyclotriphosphazatriene, N3P3Cl6, and to a lesser extent octachlorocyclotetraphosphazatetraene, N4P4Cl8, and other halogenocyclophosphazenes with primary, secondary, and tertiary amines, are described. The effect on the substitution pattern of variables such as the structure of the amine, nature of the reaction solvent, etc., are discussed in some detail. Attention is drawn to the importance of steric effects. Isomerisation reactions are referred to. The physical properties of aminocyclophosphazenes and aminohalogenocyclophosphazenes are discussed in some detail. These include basicity studies, 1H and 31P NMR and 35Cl NQR studies, Faraday effect measurements, etc. Attempts are made to correlate the above properties with X-ray crystallographic studies and quantum chemical calculations. The distinction between ground state and perturbed state properties is emphasised. Synthesis, structure, and properties of phosphazenylcyclophosphazenes and related compounds are described and a novel conformational behaviour is discussed and rationalised.