Ammoxidation of methyl N-heteroaromatic compounds was investigated on non-conventional vanadium phosphorus oxides of different origin and supported vanadium phosphorus oxide catalyst under atmospheric pressure at 400 0C. Conventional V2O5-MoO3/Al2O3 catalyst was studied for comparison under similar conditions. The catalysts were characterized by means of X-ray diffraction, electron spin resonance, infrared, scanning electron microscopy, differential thermal analysis, ammonia chemisorption and BET surface area methods. The catalytic activity is correlated well with the physicochemical characteristics of the catalyst. Higher activity for SiO2 supported VPO catalyst compared to conventional catalyst V2O5-MoO3/Al2O3 and vanadium phosphorus oxides of different origin can be attributed to high active surface area, lower oxidation state of vanadium and higher surface acidity. A redox cycle between (V4+) and (V5+) species appears to be responsible for the ammoxidation activity of VPO catalyst.