Proton dynamics in phase II of CsHSO4 have been studied by H-1 NMR. H-1 spectral line shapes were traced between 210 and 470 K, and H-1 spin-lattice relaxation curves were measured between 3 10 and 470 K, taking into account the thermal history of the sample. The NMR results demonstrate that proton transfer between two neighboring SO4 tetrahedra takes place much more easily than the reorientation of the SO4 tetrahedra in phase II. Thus, the SO4 reorientation limits the rate of the proton transport. Correlation times of the SO4 reorientation are estimate I from the second moments of H-1 NMR spectra. The obtained parameters are tau(0) = 1.5 x 10(-9) s and E-a = 29 kJ/mol. The H-1 spin-lattice relaxation in phase II is caused by motions much faster than the SO4 reorientation. (C) 2003 Elsevier B.V. All rights reserved.