The crystal structure of Li3AlH6 was investigated at high pressures upto 27 GPa using a diamond anvil cell with synchrotron radiation in addition to high temperature X-ray diffraction. Density functional theoretical (DFT) calculations were performed simultaneously. While the structure of Li3AlH6 is stable on increasing temperature, the results of high pressure experiments show a pressure induced phase transition from the ambient R3 phase to a high pressure cubic Ia3 phase around 10.6 GPa. The transition pressure of 10.6 GPa and the bulk modulus value B-0 = 32(2) GPa for the R3 phase obtained are in good agreement with the theoretical results. (c) 2008 Elsevier B. V. All rights reserved.