This work aims at studying the extensional rheological behavior of polypropylene (PP), ethylene-butene copolymer (PEB) and their blends in the melt. The weight fraction of the PEB in the blend is 20 and 40%, respectively. Dynamic mechanical analysis shows that these two blends exhibit two tand peaks corresponding to the glass transitions of the PP and PEB, respectively. Differential scanning calorimeter results indicate that the presence of the PEB does not alter the melting and crystallization temperatures of the PP. Master curves at 170 degrees C are constructed for the storage and loss modulus as well as complex viscosity. The extensional behavior of the PP, PEB, and their two blends is studied. The PEB enhances the strain hardening of the PP. Changes in the blend morphology during the extensional analysis are also studied. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers