Chemical behavior of lithium ions in reexpanded lithium-montmorillonites has been investigated, their hydration capacity, interlamellar availability, and thermal reactivity being examined. Two experiments have been carried out : a thermal treatment to evaluate the possible recollapse of the sample, and an ionic exchange with sodium ions followed by a further thermal treatment to analyze its exchange capacity. Samples obtained have been characterized by means of XRD, FTIR, DTA/TG, and Si-29, Al-27, and Li-7 MAS NMR. A complete recollapse of the sample after the thermal treatment and an extensive ionic exchange in NaCl solution were attained. The total reversibility of the process for lithium ions has been concluded, although irreversible damage in the silicate lattice is observed.