Calcium carbonate (CaCO3) particles with various shapes were prepared by the reaction of sodium carbonate with calcium chloride in the presence of a new functional double-hydrophilic block copolymer poly (acrylic acid)block-(acrylic hydroxy lactide) (PAAL) at room temperature. The as-prepared products were characterized with scanning electron microscopy and X-ray diffraction. The effects of pH, concentration of PAAL and CaCO3 on the crystal form and morphologies of the as-prepared CaCO3 were investigated. The results show that pH, concentration of PAAL and CaCO3 are important parameters for the control of morphologies of CaCO3. Depending on the experimental conditions, various morphologies of CaCO3, such as plate-like aggregates, poly-nucleated spheres, ellipsoids, monodispersed spheres, rhombohedras, etc., can be obtained. Especially, the optimal experimental conditions for the production of monodispersed spherical CaCO3 particles were determined. (c) 2005 Elsevier Ltd. All rights reserved.