In this paper, 1,2-bis (4-aminophenoxy) ethane-N, N, N', N'-tertraacetic acid (4-BAPTA) which is closely related to the common medically used Ca chelating agent BAPTA (or 2-BAPTA), was synthesized and used as an effective crystal nucleation and growth modifier to control the crystallization of CaCO3. Some important parameters, namely pH of the solution, additive concentration and CaCO3 Supersaturation, were systematically studied. Spherical vaterite and calcite with various morphologies were produced in the presence of 4-BAPTA by a simple solution synthesis. The results indicate that the 4-BAPTA effected not only the polymorph but also the morphologies and sizes of the CaCO3 crystals. (c) 2004 Elsevier B.V. All rights reserved.