A simple and controllable method was developed to synthesize large-sized hydroxyapatite (HAP) rods. Firstly, HAP crystals were reprecipitated from the supersaturated HAP solution in the presence of gelatin. After calcination at 600 degrees C for 4 h, large-sized HAP rods with good purity and crystallinity were obtained. Furthermore, due to the protection of gelatin at a high concentration, the HAP rods had a perfect monodispersity. The average length of rod-like HAP crystals could be controlled in the range of 0.65-5 mu m by simply changing the weight ratios of HAP to gelatin from 0.2:8 to 2:8. (c) 2006 Elsevier B.V. All rights reserved.