Boundary conditions for fluid-filled porous media are derived in a form independent of the choice of equations of motion. A definition of the boundary surface, together with the equation of continuity for a porous medium, leads to some of the boundary conditions. The others are suggested by the physical meaning of the various stress tensors and the porosities and the concept of the alignment. For problems of seismic transmission and reflection it is demonstrated that these boundary conditions are complete. When one of the media degenerates to an elastic solid or a fluid continuum, the boundary conditions are specialized accordingly. ¿ American Geophysical Union 1989