New technology for the hydroformylation of olefins has been developed jointly by Union Carbide Corporation, Davy Powergas Limited and Johnson Matthey & Co. Limited. The process employs a novel rhodium-based homogeneous catalyst system at significantly lower pressures and temperatures than conventinal cobalt-using processes, resulting in major savings in capital investment and operating costs. Another most important feature of the new process is that it provides much higher process is that it provides much higher ratios of normal:iso aldehydes produced when propylene and other olefins are used as feedstocks than is possible with conventional processes. Several plants utilising the new system are now under construction.