Abstract: Process for preparing primary amines from aldehydes by mixing an aldehyde with a diluent, where in the case of an alcohol or of water as diluent the mixing temperature is at most 5.degree. C. to prevent the formation of the hemiacetal or the aldehyde hydrate, and bringing the mixture into contact with a mixture of ammonia, hydrogen and hydrogenation catalyst, whereby the formation of an imine is prevented, at temperatures of from 60.degree. to 180.degree. C. and pressures of from 20 to 60 bar, at least 15 mol of ammonia being used per mol of aldehyde group, and also an apparatus for carrying out the process.