The feasibility of multidisciplinary simulations for realistic geometries involving detailed physical models is demonstrated. Specifically, a three-dimensional chemically reacting fluid flow solver is coupled with a solid-phase heat transfer solver that includes cooling channels. Both fluid- and solid-phase models employ the integral, conservative form of the governing equations and are discretized by means of two finite volume numerical schemes. To keep the heat flux consistent, a special algorithm is developed at the interface between the solid and fluid regions. Physical and thermal properties of the solid materials can be temperature dependent, and different materials can be used in different parts of the domains due to a multiblock gridding strategy. The cooling channel model is developed by using conservation laws of mass, momentum, and energy, taking into account the effects of heat transfer and friction. The coupling of the models (solid and fluid, solid and cooling channels) is detailed. A hot-air nozzle test case is examined, and the simulated results are validated by means of available experimental data. Finally, a more complex case is simulated, involving the water-cooled nozzle of a rocket-based combined cycle thruster. This case employs all three models, fully coupled. The calculated temperatures in the nozzle wall and at the cooling channel outlet are compared with experimental data and are in reasonably close agreement. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.