Solute diffusion in nematic liquid crystalline fluids has been studied
using Enskog kinetic theory and molecular dynamics simulation. The li
quid crystalline solvent is modelled by perfectly aligned hard ellipso
ids of revolution, and the solute is either a spherical or ellipsoidal
particle. The diffusion coefficient is calculated for a range of solv
ent densities and solute and solvent aspect ratios and sizes. The kine
tic theory enables us to study various parameters easily compared with
simulation or experiment. The validity of the kinetic theory, and its
range of applicability is tested against the computer simulations. Th
e main focus of the study is the anisotropy of diffusion, defined as t
he ratio of diffusivity in directions parallel and perpendicular, resp
ectively, to the solvent director. If the pair correlation function at
contact surface is taken to be isotropic, Enskog kinetic theory finds
that the anisotropy in diffusion is independent of density and collis
ion frequency, and depends only on size and shape of colliding particl
es. This result is confirmed by the simulations.