In situ high-pressure energy-dispersive X-ray diffraction (EDXRD) experiments on melamine (C3N6H6) have been carried out using diamond anvil cell (DAC) with synchrotron radiation source. In the pressure range from ambient pressure up to 14.7 GPa, two pressure-induced structure phase transitions, from monoclinic to triclinic structure at about 1.3 GPa and from triclinic to orthorhombic structure at about 8.2 GPa, are observed. The crystal structures of melamine at different pressures are built by using Materials Studio (MS) based on the principle of energy minimization. (C) 2002 Elsevier Science B.V. All rights reserved.