Abstract: A heteroaromatic nitrile is prepared in high conversion and yield by catalytically reacting an alkyl-substituted heteroaromatic compound with molecular oxygen and ammonia in the presence of a catalyst having the following composition:Mo(P).sub.x (A).sub.y (B).sub.z (O).sub.w (I)wherein x, y, z and w represent atomic ratios of phosphorus, an element A defined below, an element B defined below and oxygen to molybdenum, respectively and(i) x and z are both 0 (zero), y is from 0.1 to 5, and A is at least one element selected from the group consisting of cerium and tungsten, or(ii) x is from 0.1 to 7, y is from 0 to 5, z is from 0 to 5, A is at least one element selected from the group consisting of cerium, manganese and tungsten, and B is at least one element selected from the group consisting of thallium, titanium, niobium and aluminum, or(iii) x is from 0.5 to 7, y is from 0 to 5, z is from 0.01 to 2.