Abstract: A process of manufacturing acrylonitrile or methacrylonitrile by the catalytic reaction in the vapor phase of a paraffin selected from propane and isobutane with molecular oxygen and ammonia by catalytic contact of the reactants in a reaction zone with a catalyst, the feed composition having a mole ratio of the paraffin to ammonia in the range of from about 2.5 to 16 and a mole ratio of paraffin to oxygen in the range of from about 1.0 to 10, wherein said catalyst has the elements in the proportions indicated by the empirical formula:VSb.sub.m A.sub.a Mo.sub.b D.sub.d O.sub.xwhereA is one or more of Ti, Sn, Fe, Cr and Ga;D is one or more of Li, Mg, Ca, Sr, Ba, Co, Ni, Zn, Ge, Nb, Zr, W, Cu, Te, Ta, Se, Bi, Ce, In, As, B and Mn;m equals 0.8 to 4;a equals 0.01 to 2;0<b<0.005;d is 0 to 2;x is determined by the oxidation state of the cations present, and the catalyst has been heat treated at a temperature of at least 780.degree. C.