Structural changes of pyrochlore titanates, Sm2TiO7 and Gd2Ti2O7, at high pressures were studied by in situ Raman scattering and X-ray diffraction (XRD) methods. The Raman experiments revealed that RE2Ti2O7 lost pyrochlore structural character at pressures of 40 GPa and 38 GPa for RE = Sm and Gd, respectively. However, XRD results found that they were only partially amorphized up to 51 GPa. The crystalline phase at high pressure is a distorted pyrochlore - the anions have lost long-range order while the rare earth ions still keep some ordering. Both of the pyrochlores became completely amorphous after releasing pressure from 51 GPa. (c) 2005 Elsevier B.V. All rights reserved.