Structural changes in samarium under pressure were studied in a diamond-anvil cell (DAC) to 189 GPa. A number of phase transformations were observed between room pressure and 75GPa. At about 91 GPa samarium transforms to a body-centered tetragonal structure, and the unit cell parameters at 189 GPa are a=2.402(4) A ̊ and c=4.231(17) A ̊, V=24.40(12) A ̊3 and Z=2. Identification of a body-centered tetragonal phase in Sm at about 90 GPa, which is similar to that reported in Ce, suggests that this phase could appear in other rare-earth elements too. © 1991.