A process for the catalytic hydroformylation of olefins having from 6 to 24 carbon atoms, in which the hydroformylation is carried out in one or more stage(s) and a mixture comprising at least one olefin and an aldehyde in a molar ratio of aldehyde to olefin of from 0.005:1 to 0.2:1 is used as feed in at least one of these stages which is carried out in the presence of an unmodified cobalt complex as catalyst.