Perfluorooctanesulfonic acid (CF(3)(CF(2))(7)SO(3)H, PFOS) efficiently catalyzes the nitrolysis of hexamethyletetetramine in fluorous media, affording a good yield of the explosive HMX. The reaction can be carried out without acetic anhydride or acetic acid. The flouorous phase containing the catalyst could be easily separated and call be reused several dines without significant loss of catalytic activity.