Abstract: A process for preparing pyridine or alkyl substituted pyridines in high yield, comprises reacting a C.sub.2-5 -aldehyde, a C.sub.3-5 -ketone or a mixture thereof, ammonia and, optionally, formaldehyde, in the gas phase in contact with a fluidized or otherwise movable bed of a catalytically effective amount of a crystalline aluminosilicate zeolite catalyst in the acidic form and having a constraint index of about 1 to about 12, with an actual contact time of the reactants with the catalyst which is at least as great as said actual contact time when the reaction is conducted in a 1 inch diameter fluid bed reactor with a pseudo contact time of at least about 2.5 seconds.