Artículo de publicación ISI ; Impedance spectroscopy and nuclear magnetic resonance (NMR) were used to investigate the mobility of water molecules located in the interlayer space of Hþ – exchanged bentonite clay. The conductivity obtained by ac measurements was 1.25 10 4 S=cm at 298 K. Proton (1H) lineshapes and spin-lattice relaxation times were measured as a function of temperature over the temperature range 130–320 K. The NMR experiments exhibit the qualitative features associated with the proton motion, namely the presence of a 1H NMR line narrowing and a well-defined spin-lattice relaxation rate maximum. The temperature dependence of the proton spin-lattice relaxation rates was analyzed with the spectral density function appropriate for proton dynamics in a two-dimensional system. The self-diffusion coefficient estimated from our NMR data, D 2 10 7 cm2=s at 300 K, is consistent with those reported for exchanged montmorillonite clay hydrates studied by NMR and quasi-elastic neutron scattering (QNS).