The thermal consequences of compaction-driven groundwater flow resulting from overthrusting are studied with a two-dimensional numerical model. The model represents a foreland basin 5 km deep and 400 km wide and is used to estimate quantitatively the magnitude, direction, and thermal consequences of fluid expulsion. Model simulations in which the permeability structure is homogeneous lead to maximum Darcy velocities of the order of 1 cm/yr, temperature in the foreland increases by less than 5 ¿C. A sensitivity analysis reveals that temperature in the foreland may be increased an additional 2 ¿C by increasing porosity, speed of thrusting, or heat flow. However, if the area underneath the thrust sheet is not effectively sealed, fluid escapes upward and thermal perturbations in the foreland are negligible. Models with basal and midlevel aquifers produce maximum Darcy velocities of the order of 4 cm/yr, but temperature in the foreland again increases by less than 5 ¿C. Models in which hot fluids at depth are channeled directly upward through a high-permeability pathway can produce temperature perturbations as high as 50 ¿C, over limited areas. Modeling results suggest that the expulsion of pore fluids from orogenic zones through the process of sediment compaction is likely to produce significant thermal perturbations in adjacent forelands only over areas that are spatially restricted, or spatially and temporally restricted. ¿ American Geophysical Union 1990