In this study, large single-crystal anatase TiO2 bipyramids were first successfully synthesized using a simple hydrothermal route. The synthesized bipyramids were characterized by XRD, SEM and TEM measurements, and found that these bipyramids are highly crystalline anatase TiO2 with a size up to 3.6 mu m between the two ends. On the other hand, it was also found that the size and shape of bipyramids were significantly influenced by the pH value. Based on a series of experimental results, a possible model for the process of dissolving-coalescing-growing, has been proposed for the formation of large anatase TiO2 bipyramids. (C) 2009 Elsevier B.V. All rights reserved.