Controlled-rheology poly(1-butene) resins have been produced by chemical modification of commodity poly(1-butene) (PB-1) resins through reactive processing with an organic peroxide. Using various amounts of peroxide, samples have been produced and have been analyzed in terms of their molecular and rheological properties. Molecular weight distributions (MWD) as determined by gel permeation chromatography (GPC) indicate that polydispersity (PDI) remains approximately constant but weight-average molecular weight (M-w) decreases with increasing peroxide concentration. These trends are in agreement with predictions from a kinetic model previously developed for the production of controlled-rheology polypropylene. Linear viscoelastic measurements indicate that the modified samples are thermorheologically simple and that zero-shear viscosity decreases with increasing peroxide concentration while flow activation energy remains approximately constant. Finally, no significant variation in melting and crystallization properties was observed for the range of peroxide concentrations used. Based on these results, it is proposed that tailor-made controlled-rheology poly(1-butene) resins can be produced easily through reactive extrusion operations similar to those used for the production of controlled-rheology polypropylene (CRPP).