A commercial 10 wt% V2O5/silicated gamma-alumina catalyst has been characterized by XRD, surface area measurement and chemisorption of oxygen and ammonia and evaluated for ammoxidation of picolines from 200 to 330 degrees C after reduction at 450 degrees C in H-2 for 2 h. Chemisorption results indicate that vanadia is in a highly dispersed state in the catalyst and that temperature has promotional effect on O-2 uptake and detrimental effect on NH3 uptake. Oxygen chemisorption seems to occur in oxygen vacancies created by reduction and NH3 chemisorption seems to be structure sensitive on the catalyst at higher temperatures. The ammoxidation activity of the catalysts and yields of the nitriles increase with rise in reaction temperature up to 300 degrees C and decrease with increase in feed rate above 2 cm(3) h(-1). The catalyst exhibits the highest activity for ammoxidation of 4-picoline and the activity decreases in the order, 4-picoline > 3-picoline > 2-picoline. The activity results appear to correlate with the oxygen chemisorption capacities of the catalyst at different temperatures.