Catalytic properties of molybdophosphoric, mixed vanadium molybdophosphoric heteropoly acids H3+nPMo12-nVnO40 (n = 0, 1, 2) and their salts Na7PV4Mo8O40 and Na8HPV6Mo6O40 have been studied in methylpyrazine ammoxidation. Partial vanadium substitution for molybdenum in heteropoly acids increases activity and selectivity towards cyanopyrazine. Sodium salts are somewhat less active and selective.