In order to investigate the influence of the lateral packing modes of hydrocarbon chains on the dynamical properties of lipid compounds, we have studied the dynamics of three polymorphic phases of tristearin by using the quasielastic neutron scattering and the solid state ^<13>C NMR. It is clarified that the mobility of the acyl chains depends significantly on the lateral packing. In the a phase with loose lateral packing, large fluctuations of hydrocarbon chain about their chain axes are activated.
