This paper reports the first performance of a crystalline SbRe2O6 catalyst, which is a new family of Re mixed oxide, for the selective ammoxidation reactions of isobutylene to methacrylonitrile and propene to acrylonitrile. The SbRe2O6 with alternate (Re2O6)(3-) and (SbO)(+) layers showed much better performance than two other known Re-Sb-O compounds SbOReO4. 2H(2)O and Sb4Re2O13 with tetrahedral (ReO4)(-) anions and cationic (SbO)(+) layers. The SbRe2O6 catalyst was also much more active than a coprecipitated SbRe2Ox catalyst, a supported Re2O7/Sb2O3 catalyst, and Re oxides such as Re2O7, ReO3 and ReO2 for the selective ammoxidation. Rhenium is prerequisite to the ammoxidation catalysis of the Re-Sb mixed oxides. Sb oxides such as Sb2O3 and Sb2O4 were inactive, but Sb in the SbRe2O6 catalyst contributes positively to the methacrylonitrile and acrylonitrile syntheses. Neither change nor modification of the surface composition, crystallinity and morphology of SbRe2O6 occurred under the ammoxidation reaction conditions, where the presence of NH3 stabilized the crystalline SbRe2O6 structure.