Crystalline thermosetting blends composed of 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BA-PP)-cured epoxy resin (ER) and poly(epsilon-caprolactone) (PCL) were prepared via the in situ curing reaction of epoxy monomers in the presence of PCL, which started from initially homogeneous mixtures of diglycidyl ether of bisphenol A (DGEBA), BAPP, and PCL. The miscibility of the blends after and before the curing reaction was established with differential scanning calorimetry and dynamic mechanical analysis. Single and composition-dependent glass-transition temperatures (T-g's) were observed in the entire blend composition after and before the crosslinking reaction. The experimental Tg's were in good agreement with the prediction by the Fox and Gordon-Taylor equations. The curing reaction caused a considerable increase in the overall crystallization rate and dramatically influenced the mechanism of nucleation and the growth of the PCL crystals. The equilibrium melting point depression was observed for the blends. An analysis of the kinetic data according to the Hoffman-Lauritzen crystallization kinetic theory showed that with an increasing amorphous content, the surface energy of the extremity surfaces increased dramatically for DGEBA/PCL blends but decreased for ER/PCL blends. (C) 2003 Wiley Periodicals, Inc.