Molecular dynamics simulations on trimethylaluminum, AI(CH3)(3) (TMA), have been carried out to investigate the properties of the gas-phase dimer, the liquid, and the solid. An empirical potential model, suitable for classical simulations, has been developed. The empirical potential model captures the essential structural properties of TMA in the condensed phases and obtains fair agreement with experiments on the dimer vibrational properties. However, ab initio density functional theory based Car-Parrinello molecular dynamics simulations, performed on the TMA dimer, provide a much better representation of structural and vibrational features than the empirical model.