A new reactive extrusion process for the production of controlled-rheology polypropylene (CRPP) has been developed. Instead of the traditionally used peroxides, this process employs a photoinitiator and an ultraviolet (UV) lamp. Experiments have been carried out in a corotating intermeshing twin-screw extruder in which after mixing of the photoinitiator with the polypropylene, the melt stream is irradiated for just several seconds over two open barrel sections. Benzophonene (BP) has been used as the initiator and the effects of initiator concentration, polymer flow rate, and reaction temperature have been studied. The CRPP produced have been characterized through rheological measurements, size exclusion chromatography, differential scanning calorimetry, and Fourier transform infrared spectroscopy. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.