3-Phenoxybenzaldehyde is prepared by adding, at a relatively low temperature, a mixture of a 3-phenoxybenzyl halide and a 3-phenoxybenzal halide to a mixture of hexamethylenetetramine, acetic acid and water, the amounts of the water and acid bearing certain relationships to the amount of the mixture of halides, then heating the resulting mixture to a specified temperature level and maintaining it at that level for a specified period of time.