The gas-phase oxidation of methyl ethyl ketone (MEK) was studied on V-ZSM-5 zeolite in the presence of molecular oxygen. Two types of competitive partial oxidations, i.e., diacetyl fort-nation and oxidative scission reaction leading to acetaldehyde and acetic acid, took place at 200-350 degreesC. A detailed kinetic study was realized for the oxidation reaction, a linear relationship was observed between the conversion and partial pressure of oxygen, and an activation energy of 16 kcal/mol was encountered. The content of vanadium in the catalyst was also analyzed.