The rates of stepwise replacement of chlorine from hexachlorocyclotriphosphazene (N₃P₃Cl₆) by –NMe₂, the last chlorine atom from N₃P₃(OPh)₅Cl by alkylamines, and the first fluorine atom from N₃P₃F₆, by –NMe₂, in methyl cyanide, have been determined at three temperatures. Detailed analysis of the kinetic data suggests a concerted S_N2(P) mechanism for the first and second Cl substitutions. A sharp changeover from an S_N2(P) to an S_N1 (P) mechanism occurs at the fourth substitution; the replacement of chlorine from N₃P₃(OPh)₅Cl also occurs by an S_N1 (P) pathway. The first F substitution from N₃P₃F₆ by –NMe₂ proceeds ca. 20 times slower than the analogous reaction for N₃P₃Cl₆; the kinetic data for these two reactions are in accord with a two-step S_N2(P) pathway. Many diverse findings reported for the aminolysis reactions of halogenocyclophosphazenes are explained in terms of the continuous spectrum of mechanisms established in the present study.