We have experimentally obtained some of the parameters necessary for understanding the segregation of silicate liquid from amphibolite undergoing dehydration melting at 1 GPa and 750--1000 ¿C. The solidus for this calcic amphibolite (68% Mg-Hb, 32% Pl (An90)) is <750 ¿C. Amphibolites begin to melt at relatively high temperatures in the garnet-absent field, but the solidus appears to backbend at ~1 GPa, coincident with the garnet-in boundary. Hornblende breakdown due to garnet formation releases H2O and causes melting. Thus, in the garnet-present field (≥1 GPa), the amphibolite dehydration melting solidus may be coincident with the H2O-saturated solidus. Liquid interconnectivity may be achieved at <900 ¿C and <5 vol % liquid, based on both physical and chemical data from solid rock runs. Mass balance calculations from powdered rock runs suggest that small amounts (~5--15 vol %) of hydrous (≥4 wt % H2O), low-viscosity (103--104 Pa s), heavy rare earth element-depleted, felsic liquid may be segregated during amphibolite dehydration melting at ≥875 ¿C. The rapid breakdown of coarse-grained Hb cores may lead to the formation of transient H2O-saturated liquids with even lower viscosities (~102 Pa s). Although comprising only a small portion of the melting cycle, these H2O-rich conditions may enhance the segregation of liquid by reduction of liquid viscosities and by mechanical effects on the restite (e.g., increased deformation and liquid fracturing). During anatexis of coarse-grained (natural) rocks, transient conditions may control the initial stages of liquid segregation. ¿ American Geophysical Union 1995