Preliminary experiments were made to determine the partition coefficients of rare earth elements between garnet and liquid at 30 kb and 1275¿C in the system diopside (30 wt%) -pyrope(70%) -water. REE were added to the system by titration at concentration levels in the range of natural basalts. The phases were separated by differential dissolution technique (DDT) and analized for REE by isotope dilution. The partition coefficients (solid/liquid) are: 0.021 for Ce, 0.087 for Nd, 0.217 for Sm, 0.320 for Eu, 0.498 for Gd, 1.06 for Er and 4.03 for Yb. They are in excellent agreement with those estimated from cpx-liq and cpx-gar relationships currently used in the literature.