Cross-polarization efficiency was shown to reflect the phase transitions of phospholipid bilayers. A quantitative analysis of the cross-polarization dynamics in dipalmitoylphosphatidylcholine bilayers was carried out and the efficiency was interpreted in terms of the cross-relaxation time and the spin-lattice relaxation time of protons in the rotating frame. Except for the subgel phase, the cross-relaxation time was shown to be orientation dependent and to reflect the fluctuation of the director of the polar head group. Temperature dependence of the spin-lattice relaxation time in the rotating frame showed characteristic changes at the sub-, pre-, and main transitions, respectively. The change of cross-relaxation time and chemical-shift anisotropy at the pretransition clearly showed that the pretransition significantly affects the dynamic state of the polar head group.