We report two separate synchrotron FTIR measurements of the high explosive HMX at ambient temperature and static high pressure in the far- (100-500 cm (1)) and mid-(500-3200 cm (1)) infrared (IR) regions up to similar to 30 GPa. The sample for the far-IR experiment was loaded with no pressure-transmitting medium and the sample for the mid-IR study utilized a KBr pressurizing medium. Two possible phase transitions were observed near 5 and 12 GPa (likely into the is an element of phase). A phase transition was observed near 25 GPa probably into the delta phase. Pressure cycling in both experiments found no irreversible damage within this pressure range. (C) 2010 Elsevier B.V. All rights reserved.