Abstract: There is described an improved hydroformylation process in which an alpha-olefin is converted to aldehydes by feeding the olefin, carbon monoxide and hydrogen to a homogeneous liquid phase composition containing a catalytic amount of rhodium carbonyl complexed with a triarylphosphine which is provided in an amount greater than that which complexes with said rhodium carbonyl, a substantial amount of condensation products of said aldehydes and said aldehydes. The improvement involves providing a sufficient amount of oxygen to said liquid phase composition whereby to maintain a desired aldehyde productivity during the operation of said process.