A comparative study has been performed of the reactions of nitric oxide (NO), nitrogen dioxide (NO 2), nitrosyl fluoride (FNO), nitryl fluoride (FNO 2), and nitrogen oxytrifluoride (F 3NO) with the hexafluorides of uranium, neptunium, and plutonium. Significant chemical differences among the hexafluorides were found. Thus, UF 6 and excess NO reacted at room temperature to form the nitrosonium salt (NO)[UF 6], the same U(V) product formed from the reaction of UF 6 with excess NO 2. Excess NO reacted rapidly with NpF 6 to form poorly crystalline Np(IV) solids, but with an equimolar amount of PuF 6 at reduced temperature NO reacted to yield a mixture of Pu(IV) species and the new compound (NO)[PuF 6]. With NpF 6, FNO reacted only under photolytic conditions to give (NO)[NpF 6], whereas PuF 6 oxidized FNO to give F 3NO and a mixture of (NO)[PuF 6] and Pu(IV) solids. No reaction was observed between NpF 6 or PuF 6 with FNO 2. Likewise, no reaction was observed between F 3NO and the actinide hexafluorides, even under photolytic conditions.