Evolution of the poly(epsilon-caprolactone) (PCL) lamellae in blends of PCL/PC (polycarbonate) was monitored by synchrotron small-angle X-ray scattering(SAXS). The effects of crystallization temperature, PC concentration, and PC crystallinity on the PCL lamellar growth in the PCL-rich blends were investigated. The half-crystallization time derived from the temporal change of the peak intensity increased with crystallization temperature and generally increased with the addition of PC. For a given blend composition, the lamellar growth rate increased with increasing PC crystallinity. The interlamellar spacing initially varied with time and then approached a plateau value at the later stage of crystallization. An insertion mechanism is proposed in which the PCL is crystallized in the amorphous intralamellar phase. This model is also consistent with the quantitative SAXS results,6 which suggested that random mixing of PCL and PC lamellae occurred in the semicrystalline (PCL)/semicrystalline (PC) state.