Nonisothermal and isothermal crystallization behaviors of the hyperbranched poly(e-caprolactone) (HPCL)/poly(vinyl chloride) (PVC) and linear poly(epsilon-caprolactone) (LPCL)/(PVC) blends were characterized with various blend composition such as 100/0, 95/5, 90/10, and 80/20, respectively. HPCL was synthesized through polycondensation of AB(2) macromonomer while LPCL and PVC were commercially purchased. The architectural characterization performed on H-1 NMR spectra revealed that HPCL consisted of about 3 AB2 units and the linear segments consisted of 25 e-CL units. Through the nonisothermal crystallization analyses by modified Avrami approach with DSC crystallization exotherms, it was found that the crystallization rate was retarded by the increase in the noncrystallizable component (PVC) in the blends. This is in good agreement with the results of the isothermal crystallization analyses where time resolved small angle light scattering (SALS) and polarized optical microscopy (POM) were used. The effect of molecular architectural difference between HPCL and LPCL on the crystallization of their binary blends with PVC was elucidated by comparing the crystallization kinetic parameters. Both the nonisothermal and isothermal crystallization analyses showed that the crystallization rates of HPCL/PVC blends was faster than LPCL/PVC blends at given blend compositions. The faster crystallization of the HPCL/PVC blends is ascribed to the two specific architectural characteristics of HPCL; the branched structure and the incorporated long linear segments. (c) 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 577589,2007.