Molecular dynamics (MD) simulations are used to investigate the properties of an atomic model of an aromatic polyamide reverse osmosis membrane. The monomers forming the polymeric membrane are cross-linked progressively on the basis of a heuristic distance criterion during MD simulations until the system interconnectivity reaches completion. Equilibrium MD simulations of the hydrated membrane are then used to determine the density and diffusivity of water within the membrane. Given a 3 MPa pressure differential and a 0.125 mu m width membrane, the simulated water flux is calculated to be 1.4 x 10(-6) m/s, which is in fair agreement with an experimental flux measurement of 7.7 x 10(-6) m/s.