A catalytic composition useful for the conversion of an olefin selected from the group consisting of propylene, isobutylene or mixtures thereof, to acrylonitrile, methacrylonitrile, and mixtures thereof. The catalytic composition comprises a complex of metal oxides comprising bismuth, molybdenum, iron, cerium and other promoters, wherein the ratio of bismuth to cerium ratio in the composition is greater than or equal to 0.45 and less than or equal to 1.5.