The crystallization behavior of poly(E-caprolactone) (PCL) blocks starting from a solid lamellar morphology formed in advance by the crystallization of polyethylene (PE) blocks (PE lamellar morphology) in a PCL-b-PE diblock copolymer was investigated by differential scanning calorimetry (DSC), small-angle X-ray scattering with synchrotron radiation (SR-SAXS), and polarized optical microscope (POM). The crystallization behavior was quantitatively compared with that of a PCL-block-polybutadiene copolymer, where the crystallization of PCL blocks started from a rubbery lamellar microdomain. DSC and SR-SAXS results revealed that the crystallization rate of PCL blocks in PCL-b-PE increased drastically with decreasing crystallization temperature T-c and the Avrami exponent depended significantly on T-c. SR-SAXS curves during the crystallization of PCL blocks at high T-c showed a bimodal scattering character, that is, the peak position moved discontinuously with crystallization time. At low T, on the other hand, no shift of the SAXS peak position was observed. The macroscopic change in morphology was detected only at high T-c by POM observations. These experimental results for the crystallization behavior of PCL blocks in PCL-b-PE all support our previous conclusions obtained by static measurements the crystallization mechanism at low T-c is completely different from that at high T-c that is, the PCL blocks crystallize within the PE lamellar morphology at low T-c. while the crystallization of PCL blocks at high T-c yields a morphological transition from the PE lamellar morphology into a new solid morphology. © 2005 Elsevier Ltd. All rights reserved.