Some metal vanadates were precipitated as the pure phases by adjusting the pH of aqueous solutions of the raw materials. The precipitates were calcined at 550 o C and tested for the vapor phase oxidation of 3-picoline to nicotinic acid. Chromium vanadate showed the highest activity among the vanadates tested; its structure belongs to monoclinic CrVO 4 -I. An addition of aluminum into CrVO 4 -I resulted in the formation of the solid solution of Cr 1 - x Al x VO 4 still keeping CrVO 4 -I structure with high surface area in the range of x=<0.5. Upon further addition of aluminum, CrVO 4 -I structure changed to AlVO 4 structure. The activity increased with increasing the Al content while keeping CrVO 4 -I structure; the highest activity was obtained at x=0.5. In the CrVO 4 -I structure, all the V species are isolated as VO 4 tetrahedra and show the oxidation activity via its redox properties. NH 3 -TPD results showed that acidity increased by the replacement of Cr with Al in CrVO 4 -I. The addition of a large amount of water in the reaction mixture enhanced the yield of nicotinic acid. The highest activity was obtained over the Cr 0 . 5 Al 0 . 5 VO 4 and the total yield of nicotinic acid and pyridine-3-carbaldehyde reached to 69% (selectivity, 86%) at 350 o C. Thus, 3-picoline can be effectively oxidized with O 2 in the gas-phase to nicotinic acid on the Cr 0 . 5 Al 0 . 5 VO 4 catalyst having Bronsted acid sites in addition to redox properties.