Acetaldehyde is prepared from methanol and synthesis gas with good selectivity and yield by contacting a mixture of methanol, carbon monoxide and hydrogen with an iodide or iodine free catalyst composition comprising (1) ruthenium powder, (2) a cobalt-containing compound, (3) an amine, and (4) an onium salt or base, and heating the resulting mixture to an elevated temperature and pressure for sufficient time to produce the desired acetaldehyde, and recovering the same from the reaction mixture.