The equation of state and optical absorption of condensed Xe have been measured in a diamond-anvil cell up to 172 GPa. Pressures were determined by use of the ruby-fluorescence technique or from the equation of state of the Re gasket used to confine the sample. Xe transformed to an hcp structure between 70 and 90 GPa that remained stable to 172 GPa. At 150 GPa we observed sudden changes in absorption and reflection spectra of Xe that we attribute, on the basis of electron band calculations, to the onset of metallization. © 1989 The American Physical Society.