Micrometer-sized CaCO3 hollow sphere has been synthesized by the reaction of sodium carbonate with calcium chloride in the presence of sodium dodecyl sulfate (SDS) and the triblock copolymer Pluronic F127. SEM and XRD investigations indicate that such hollow superstructure is aggregated by calcite nanoflakes. SAED pattern suggests that the individual calcite nanoflake is single crystalline. SEM images of products collected at different periods and the XRD result of product formed at the early period suggest that hollow CaCO3 microspheres are fabricated through self-transformation associated with the Ostwald ripening process. The attractive hydrophobic interaction between the alkyl group of anionic surfactant and PPO block of F127 plays an important role in the fabrication of hollow structure. (C) 2007 Elsevier Ltd. All rights reserved.