This work is an ongoing experimental research program designed to provide data on the variables controlling the mechanical behavior of partially molten systems within the crust. The specific problem to be investigated is the production of granitoid melts by ultrametamorphism of metasediments, and it is expected that the results will provide a new dimension to the interpretation of field occurrences of migmatites and granites. A primary objective is to determine how the amount and composition of melt produced varies with temperature, pressure, and the bulk composition of the staring material. Experiments designed to investigate the melting behavior of layered metasediments are also planned and the implications of all experiments for metamorphic temperature and pressure will be evaluated.