The influence of high content of MoO3 (32 mol%) in V2O5-MoO3-P2O5 catalyst system supported on alumina, silica, HZSM-5 and modified clay was investigated for ammoxidation of 3-picoline. Unsupported VMPO catalyst and supported catalysts were prepared by incipient wet impregnation method keeping the mole ratio of V2O5-MoO3-P2O5 (1.00:3.27:0.14) constant. FT-IR spectra and X-ray diffractograms showed interaction among the active oxides and the support. The major phases identified were Mo4V6O25, Mo6V9O40 and MoV2O8. TG-DTA also showed the exothermic peaks indicating the formation of new compounds above 400degreesC. The physico-chemical properties of the catalysts were correlated with their activity and selectivity for ammoxidation of 3-picoline. The unsupported catalyst showed 96.0% selectivity whereas VMPO/HZSM-5 showed the highest selectivity (91.3%) amongst the supported catalysts. (C) 2004 Elsevier B.V All rights reserved.