The ammoximation of methyl ethyl ketone and hydrogen peroxide to form methyl ethyl ketoxime was studied over zeolites (TS-1) in the temperature range 308-373 K. The reaction was carried out in a batch autoclave at autogenous pressure. The conversion of methyl ethyl ketone and the selectivity to methyl ethyl ketoxime can reach 99% and approximately 100%, respectively, and the by-products were the small amounts of corresponding methyl ethyl ketazine and trace amounts of unidentified compounds. Important factors were the reaction temperature, solvents and slow addition of hydrogen peroxide. The molar ratio of NH3 to ketone had no significant effect on the conversion of methyl ethyl ketone, but increase in the ratio of NH3 to ketone had a beneficial effect on selectivity. (c) 2006 Society of Chemical Industry.