The common occurrence of high-pressure tectonic terranes along the Pacific coast and other convergent origins suggest that the evolution of subduction complexes may be an important phase in the development of continents. In this study we model the steady state thermal structure in an active subduction complex. Following Cloos, we treat the movements of sediments in deep subduction complexes as laminar flow in a viscous fluid. Driven by the descending plate and blocked by the hanging wall of the nonsubducted plate, a part of the sedimentary pile is forced to convect. Temperatures in subduction complexes are determined by the velocity of flow, radiogenic heating, and heat flow across the boundaries of these complexes. Heating becomes important when the rate of flow is small, of the order of 10 mm yr-1. Under such conditions, temperatures in subduction complexes are suitable for the formation of the characteristics metamorphic facies and may lead to the progression in metamorphic age and grade observed in many high-pressure tectonic terranes. Fast convection cools the accretionary prisms; convective cooling can be so effective that temperatures even in the deepest interiors of subduction complexes may become too low for the formation of the metamorphic mineral assemblages that are currently used as criteria to identify sediments that experienced deep burial in the past. The results of this study suggest that thermal modeling and prediction of the distribution of metamorphic grades and ages of sediments in subduction complexes can provide powerful tests on hypotheses on the evolution of these complexes.