A new vanadium resin catalyst has been prepared through ion exchange at the cationic sites of Amberlite IR 120 resin. This vanadium-loaded resin is characterized by using AAS, UV-vis, FTIR and EPR spectroscopic tools. Ammoximation of cyclic ketones e.g. cyclohexanone, cyclooctanone and cyclododecanone in the presence of aqueous hydrogen peroxide and ammonia have been carried out under eco-friendly liquid phase conditions over this vanadium resin at 333 K. Interestingly, for ammoximation of cyclohexanone the progress of the reaction could be visually monitored from the change in color of the catalyst during the reactions: after the consumption of H2O2 the orange catalyst returns back to its original green color. For all the cyclic ketones corresponding oximes are obtained as major products with moderately high yields. The new catalytic system described herein is an efficient and eco-friendly method for the ammoximation of bulky cyclic ketones, with the advantages of good conversion and selectivity, devoid of hazardous solvents and byproducts. (C) 2008 Elsevier B.V. All rights reserved.