The purpose of this work is to evaluate a new polypropylene (PP)-based nitroxyl radical generator (NOR) and offer comparisons with a commonly used peroxide in the production of controlled-rheology polypropylene (CRPP) resins. CRPP resins are produced by reactive processing in a batch mixer by using different amounts of either the NOR or a peroxide initiator at different temperatures. Molecular weight and rheological properties are determined for all CRPP produced and a comparison between the effectiveness of the NOR and the peroxide initiator is provided. POLYM. ENG. SCI., 47:2118-2123, 2007. (C) 2007 Society of Plastics Engineers.