The high-pressure phases of tin have been studied by energy-dispersive x-ray diffraction to 120 10 GPa at room temperature in a diamond-anvil cell. The body-centered cubic structure, evolving from the body-centered tetragonal structure at 45 5 GPa, is found to be stable to the highest pressure of 120 GPa. Along with previously published data, the present results complete the equation of state of tin to 120 GPa at room temperature. The stability of the bcc phase is discussed in the broader perspective of the pressure behavior of the other Goup-IVA elements and the isoelectronic III-V compound InSb. © 1989 The American Physical Society.