Equilibrium NPT and NVT molecular dynamics simulations were performed on liquid benzene over an extended range of temperature (from 260 to 360 K) using the COMPASS force field. Densities and enthalpies of vaporization (from cohesive energy densities) were within 1% of experiment at all temperatures. tumbling and spinning rotational diffusion coefficients, D-perpendicular to and D-parallel to, computed as a function of temperature, agreed qualitatively with the results of earlier reported experimental and computational investigations. Generally, it was found that D-parallel to/D-perpendicular to approximate to 1.4-2.5 and the activation energy for tumbling was significantly greater than for spinning about the C-6 axis [E-a(D-perpendicular to) = 8.1 kJ mol(-1) and E-a(D-parallel to) = 4.5 kJ mol(-1)]. Calculated translational diffusion coefficients were found to be in quantitative agreement with experimental values at all temperatures [deviations were less than the scatter between different reported measurements]. In addition, translational diffusion coefficients were computed in the molecule-fixed frame to yield values for D-xy (diffusion in the plane of the molecule) and D-z (diffusion perpendicular to the plane). It was found that the ratio D-xy/D-z 2.0, and that the two coefficients have roughly equal activation energies. This represents the first atomistic molecular dynamics study of translational diffusion in the molecular frame.