Abstract: The present invention relates to a continuous two-phase hydroformylation process for the production of aldehydes from olefins by means of carbon monoxide, hydrogen and a transition metal catalyst in a reaction zone, the transition metal being in the form of a water-soluble catalyst complex, wherein the process comprising the following steps once or several times: a) hydroformylating by reacting the olefins, carbon monoxide and hydrogen over a water-soluble transition metal catalyst comprising water-soluble organophosphorus ligands in the reaction zone; b) reducing the concentration of the olefins in the reaction zone by reducing the olefin feed to the reaction zone and withdrawing at least a portion of the catalyst solution from the reaction system, wherein the catalyst solution withdrawal and olefin concentration reduction substeps may occur in this or reverse order, simultaneously or sequentially; c) feeding a solvent, a transition metal source and water-soluble organophosphorus ligands to the reaction sy