The chemical behavior of crystalline Al(OH)(3) samples is governed by the lateral-to-basal surface ratio. For well-crystallized gibbsite samples possessing the two types of surfaces clearly spatially separated, a vibrational component at similar to 3460 cm(-1) in the infrared absorption spectra, not displayed in the Raman spectra, increases linearly with the lateral specific area determined by a gas adsorption isotherm. This intense and broad line is related to hydroxyl stretching modes of AlOH21/2+ or AlOH1/2- species present on the edge faces. However, it is too simplistic to assign this band to a mode of one or the other of these species. More complex structures combining both species should also be considered. When an evacuated sample is submitted during a short time to a D2O vapor injection, the OD spectral region displays essentially one broad component at 2563 cm(-1), corresponding to the 3460 cm(-1) band in the OH region and not to the other modes of the bulk hydroxyls. This experimental observation is also in agreement with the assignment of this infrared band to reactive superficial species.