Molecular dynamics computer simulations are used to study diffusion of monolayer octamethylcyclotetrasiloxane and cyclohexane films confined between atomically structured uncharged mica surfaces. Diffusion parallel to the walls is found to be anisotropic due to the influence of the atomically structured surfaces. If the surfaces are aligned perfectly the fluid occupies isolated regions of the pore space and diffusion is the same in all lateral directions and is a minimum. If one of the surfaces is shifted laterally in the x-direction by one-half unit cell diffusion is enhanced in the x-direction along conduits formed by the overlapping potential energy fields of the surfaces. This work augments earlier work by the authors and confirms that diffusion of a confined simple fluid in a nanoscale slit-pore is tunable in terms of direction and magnitude through control of the relative alignment of the surfaces. (C) 2003 American Institute of Physics.